Technical

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Wet Sumping

posted 6 May 2012, 01:41 by NOC NSW


Lifted from the Made in England email list

The gear pump in a Commando would be the simplest form of pump ever. Just around and around, even the plunger pumps in Matchy singles is more complex, combining rotary motion with reciprocating motion. An efficient gear pump must have very fine tolerances. Very fine tolerances between the gear side faces and the pump case end plates. As well there must be a very fine tolerance between the gear teeth and the case past which the teeth pass. Shaft sealing must be spot on. In bigger pumps the shaft can have lip seals and the endplates can also have seals, sealing up against the gear side faces. The tolerance between the radial end tips of the gear teeth and the case must be as fine as possible. The next best pump after a gear pump is a vane pump whereby instead of teeth the rotor has vanes that actually contact the housing as they rotate. They even get forced out by oil pressure and centrifugal force. 
      
No such luck with gears. You got wot you got, thats it. You can get a brand newy, but being so small, it's only as good as whoever made it. Bottom line here is, the hot thin oil after a good ride will slip easily past most Norton gear oil pump gear sets and dribble off into the sump. The oil will go the way it should, and that is through the pump to the crank and out through the big ends. There are gaps big enough so that over the period of a week or two you will lose the contents of the oil tank into the sump. Both my Commandos would do it over a period longer than two weeks, the Model 18 does it almost over night. 

There are taps and ball valves and all sorts of goodies to help the inept. 

I've got one on the Model 18, wouldn't dream of it on the Commando. The Commando needs oil pressure because it has plain bearing big ends, the Model 18 has rollers all the way and needs bugger all oil pressure. I've forgotten to turn the tap on, on the Model 18, nipped it up and got away with it. Just nipped the piston to bore. Oil starvation on the Commando would mean instant disaster and a major engine rebuild, as the plain bearing big ends would sh*t themselves in a big way. They definitely need oil, it's their nature. Balls and rollers can get away with it. 

What happens if all the oil drains into the sump and, so what if it does............... 

With a sump chockers with oil it's hard to imagine the engine will seize. So you wouldn't worry too much there. Sumps need to be a specific size. In a wet sump engine like most cars, the sumps are huge and the crank doesn't spin in the oil, it spins above the oil. In a dry sump engine such as most Brit bikes, there normally is no oil in the sump except half a cup ful of transient stuff on it's way back to the tank. So, in a dry sump engine there is really only room for the crank and not much anything else, including oil and including air. If you imagine your pistons going up and down, from the underside, they will be displacing quite a bit of air. Almost as much as the nominated capacity of the engine. It's like an air pump in there, pushing and sucking as the pistons go up and down. As the pistons approach BDC all the air is shoved out of the way, as the pistons return up to TDC, the air is sucked back in. This is why we have crankcase breathers on our engines, sucking and blowing, in and out. If the sump is big enough, should I say, if the volume of air contained by the sump is big enough, it will compress to a certain extent and absorb the space occupied by the pistons on their upward and downward journeys. The air will be getting compressed. The bigger the sump, or the better and bigger the crankcase breathing, the less adverse affect this suck and blow will have on the engine. 

If you have a smaller sump, or reduce the air space, then there is less space for the suck and blow to happen. Think about allowing the contents of your oil tank to drain into the normally dry sump. Oil will not compress very easily. The sump, now partially full of oil has lost probably half it's capacity to absorb the suck and blow from the pistons as they go up and down. The blow side of things as the pistons come downwards will compress the limited airspace and will want somewhere to push the air and oil out of it's way!!!! It will look for the weakest point, especially if the oil in the sump is also covering the breather outlet / inlet. Like the breather in the very bottom of the crankcases on a Combat engine!!!! Why did they move it back up to a higher point in the back of the timing chest a la 850's????????? I wonder!!!!! 

In most cases the weakest point will be the crankcase seal behind the drive sprocket. The crankcase compression will easily push that out of the way, dumping the oil from the sump into the primary. First thing you will notice is a slipping clutch as everything in there gets over-lubricated. Next you'll probably wonder why your bike suddenly needs oil, so naturally, you top it up, only to have it drain into the primary again. Bike will also probably blow smoke and try to run like a dog as well. Major dramas eventuate. Other weak spot is to blow the camshaft oil seal out, then try for the sealing surfaces such as through the vertical split in the cases or blow out a cylinder base gasket. 

What to do..........accept the fact that you ride an old pommy bike that not only has a stuffed oil pump, but it was probably like that from new and either go buy a new one and experience the same thing again or get on with your life and adapt. 

Hints & Tips 

Before going for a ride, amongst all the other things you check......check the oil level. If oil level is above half, your pretty well OK. If oil level is half way down the dip stick, start the bike carefully and don't rev it, just set on a slightly fast idle to warm up and gently pump all the oil back from sump to tank. Be gentle with it and don't give it heaps of revs, you don't want to blow that seal!!. If the oil level was further than 1/2 or off the dipstick all together. Get your clean oil drain pan and drain the oil from the sump. Ignore the fact that there was three litres in the sump. Just go make yourself a coffee and sit and chat to the trouble and strife for a while. Go back to the bike, tip the drained oil back into the oil tank, screw the sump plug in and go for a ride. 

Come to terms with the fact you are riding a bike with an oil pump and lubrication system that was designed circa 1930, get over it and don't expect to be riding around on something with the oil pump performance of a Jap bike from 1962, it's just not like that. Develope a little system for yourself. If checking and draining the oil was the very first thing you did when the idea for going for a ride entered your brain, then by the time you scratched around and donned relevant bike clobber it would only take a moment to tip the oil from the bottom, back in the top, screw in the screw and take off. You only need to drain most of it out, not every last livin drop!!! This will only take 5 mins. 

Resume Lotus position close eyes hold fingers in a funny circle thingy and repeat ........... hhhhuuuuuuuuummmmmm ..........hhhhhhhhhhhuuummmmmmmmmmmmmmmmmmmmmmmmmmmmm I love my Norton, I love my Norton, I love my Norton. 

As far as I know, the Mk3 850's are the only twins to have a check valve. Interestingly I have a single (ES2) timing cover from 1961 which has the  design check valve in it as the 1976 Mk3 850. All the rest rely on close tolerances to "hinder" bypass leakage. 

The aftermarket in line check valves are fitted to the pump suction hose between the oil tank and the pump. They have a ball and a spring inside then, the spring holding the ball on a seat against the flow of oil from the tank. This idea relies on the spring being very weak, as vrtually all it resists is the head pressure of the oil from the tank to the valve. This is the pressure created by gravity acting on the weight of oil between the difference in vertical height between the check valve and the highest level of oil in the tank. As soon as the pump starts to work a partial vacuum is created in the hose between pump and check valve. The weight of oil in the line above the check (head) is then supplemented by atmospheric pressure that balances the partial vacuum in the line below the check and forces the spring ball off it'd seat back against the spring and allows oil flow. It really doesn't take much in the way of crud etc to stall the opening of this ball check and either not allow oil past or restrict the flow enough, especially at high revs, to damage the motor. As someone else said, they do seemingly have a good record, although when one fails, kiss your engine goodbye!!!


The Mk3 Commando check and the check in the timing cover of the 1961 ES2 I have, is positioned in the timing cover on the pressure side of the pump, in the gallery that leads from the pump pressure outlet to the pressure relief valve and banjo bolt to the top end, and of course to the crank. 

When the motor is stationary, the head of oil leans on this ball, which can have a much stronger spring. The oil dribbles down it's usual path through the hose to the pump around the gears and out into the gallery in the timing case. Now, instead of continuing on to the big ends where it leaks into the sump, it is stopped in it's tracks by the ball check in the gallery. 

Being on the pressure side, and as everyone knows, a Commando can achieve big oil pressures on startup, the full pressure force of the pump pushes the ball check out of the way. Even if there was some crud behind the ball, the average oil pressure of, say, 40 psi, is much much greater than the pressure exerted on the inline ball check by the head weight of the oil alone. 

The gremlin in the woodpile here is the condition of the shaft sealing in the pump, because the Mk3 style check is after the pump and this leaves the integrity of the pump itself in question. 

Some people use little shut off valves in the suction line, as I have on my Model 18 and rig up all sorts of inventions to remind them to turn the damn thing on before they start the engine. 

In the end.........choose your own poison. 

Bob

Fri Sep 7, 2007 3:15 pm

Norton Commando Bearings

posted 25 Dec 2011, 05:07 by NOC NSW   [ updated 25 Dec 2011, 05:07 ]

Ordering bearings...

When you read "1 of 6203 17 X 40 X 12 Single Row Deep groove Ball" this means, that you need one bearing 6203, which is of the dimensions 17 X 40 X 12 and is a Single Row Deep groove Ball.

6203 is a universal number for this bearing size no matter what the brand. So you can ring up your local bearing place and say, "have you got a 6203", and be confident that it will fit, and that they will know what you are talking about.

If you want a sealed bearing this is the moment to add that info. Saying 2RS after the 6203 will get yo a bearing with a rubber shield on both sides, prepacked with grease.

While the size will remain constant the quality may differ. You will not go far wrong using the big names, NSK, FAG, SKF, RHP etc. All bearings are stock off the shelf sizes and should be available through any bearing distributer. When buying bearings get out the yellow pages and get prices from as many distributers as possible, also make sure you check with your Norton dealer as some of the more obscure sizes may be cheaper as a genuine spare part, because of the quantity used by Norton. It's up to you which bearing brands you use, but there is no or very little difference between top brands.

Front Wheel

1 of 6203 17 X 40 X 12 Single Row Deep groove Ball. You can use a sealed bearing. 
1 of 4203 17 X 40 X 16 Double Row Deep Groove Ball, sealed are rare.

Rear Wheel (true for post boltup and pre MKIII)

Wheel Hub

2 of  6203 17 X 40 X 12 Single Row Deep groove Ball, sealed if you want

Brake Drum

1 of 4203 17 X 40 X 16 Double Row Deep Groove Ball,  sealed are rare

Steering Head

2 of 6205, 25 X 52 X 15 Single Row Deep groove Ball, sealed.

Engine

Crankshaft

2 of NJ306E C3, 30 X 72 X 19 Cylindrical Roller Bearing, double lipped outer race, single lipped inner race, preferably brass caged, although polyamide cages are becoming more frequent. These are the so called 'Superblend' bearings. This bearing can be bought from any of the manufacturers (ie not just FAG) with a choice of cages ie. brass, steel, polymide.

Gearbox

Mainshaft

1 of RLS 5 2RS, 5/8 X 1 9/16 X 7/16 Deep Groove Ball, shielded, take the rubber shield out of the side facing inside the gearbox to allow gearbox oil flow (Note: not metric, imperial bearing size)

1 of RLS 9 2RS,  1 1/4 X 2 1/2 X 5/8 Deep Groove Ball, sealed, take the shield out of the side facing inside the gearbox to allow gearbox oil flow. (Note: Imperial bearing size)  Also, IMPORTANT;  the RLS 9 is listed in most catalogues as having a 1 & 1/8 bore, however get your dealer to have another look as they are also listed as having a 1 & 1/4 bore, which is what you need. They also sometimes bear the number 1654. Not every manufacturer will do them.  One manufacturer who does them is KSK. Another is RHP. This variant of the RLS 9 may have been commissioned just for Norton so availability will be relative.

Lay Shaft

The bikes were manufactured using; 1 of 6203 17 X 40 X 12 Single Row Deep groove Ball. This must be replaced by; 1 of NJ203, 17 X 40 X 12 (sometimes sold as a C3 clearance) Cylindrical Roller Bearing, double lipped outer race, single lipped inner race, you'll most likely get a polyamide cage from FAG, other materials available from other manufacturers. Polyamide cages are single use in this application as heating the box to remove them damages the polyamide.

Clutch

1 of 6007 Single Row Deep groove Ball, metal sealed, leave seals intact.

With the exception of the RLS 9 in the gearbox, all bearings are stock off the shelf sizes and should be available through any bearing distributer and will be made by any bearing manufacturer eg, NSK, FAG, SKF etc etc.

When buying bearings get out the yellow pages and get prices from as many distributers as possible, also make sure you check with your Norton dealer as some of the more obscure sizes (RLS9) may be cheaper as a genuine spare part, because of the quantity used by Norton. It's up to you which bearing brands you use, but there is no or very little difference between top brands.

This information supplied by:
Bob Davis, Hunter Valley Norton Owners Club

Norton Commando Master Cylinder Modification

posted 25 Dec 2011, 05:04 by NOC NSW   [ updated 26 Apr 2012, 04:58 ]

There are a number of ways to improve the disc brake on a Commando.

1) Fit a 1/2" mastercylinder from another brand of bike. 

2) Buy an aftermarket Lockheed or similar calliper and/or disc.

3) Sleeve your mastercylinder to 1/2".

4) Get a 11mm conversion from the US or a 1/2" sleeve job from the UK (See the bottom of the page)

I would recommend Vintage Brake in the US for interesting info, on drum brakes as well.

An approach to 3) follows.....

I need to make a point regarding liability. I am not an engineer. I have no qualifications or experience of engineering. If you are interested in following this modification you must get it checked by a qualified engineer who can certify that it is safe. Do not do it otherwise.

A number of people have been been in touch with me over the last couple of years in regard to the master cylinder brake modification sleeving  it to 1/2 inch as detailed in Classic Motorcycle Mechanics.

Here follows the simple version...

The original Lockheed master cylinder as fitted to Norton Commandos from 1972 (and to some Ducatis) was given a 5/8 bore for reasons which only promote cynicism and do not bear repeating here. The end result was the brake did not work very well. The lever felt very wooden, and it was hard to get enough braking from it.

I decided to try and improve the hydraulic advantage by sleeving the master cylinder down. I had experienced good results with a 1/2 inch Grimeca cylinder on a Norton so took that size as a reasonable objective.

Having heard of seals from a 1980s Kawasaki GPZ 500 (EZ500 in some countries) being used for the this purpose I took that as a starting point. I obtained a M/C from one and drew up a piston which had the shape and width of the Kawasaki piston but otherwise the length of the Norton.

 Click for larger image

My master cylinder  was sleeved in stainless steel. If using SS, and I would recommend it,  the piston should be made from something hard but not SS. I recommend Aluminium Bronze 3. (As a friend said, AB3 will still be there when the Vogons invade Earth) Do not use soft alloys. While they may stand up to the wear inside the cylinder they will pickup and smear at the contact point with the lever. There is no reason why the cylinder could not be sleeved in aluminium just as original, and the piston made in steel. But if you think about it those materials were chosen for poor reasons and we can do better. Why put steel in a rust prone environment?

 Click for larger printable image of piston design

The piston is a fairly straightforward turning job. The Kawasaki seal kit number is  43020-1098.  This may be an Australian part number, it's from a GPZ 500 from early eighties, single disc type. In the US this bike was called an EZ 500. 

In the kit you get a piston, seals and spring. Biff the piston and use the seals and spring. If you need a new boot and spring clip they are available from the usual sources of Norton parts.   

The original cylinder had a trap valve in the same end of the bore to slow the fluid in the downward direction (ask yourself, why would anyone make the brake slow to act? No, don't. ) Leave this out.  It wouldn't fit the smaller bore anyway. With this exception,  assembling the brake is exactly as for the standard setup. If anything about your setup is not standard, for example the calliper, or the lever (any change to the lever is significant, mail me if you need to  know why), deep thought may be needed.

While I have not struck problems in those I have assembled personally or heard of any problems with  the many assembled to these instructions elsewhere there is need to be cautious . There are variations to dimensions in the original casting, for example I am told there is up to 160 thou difference possible in length of the internal bore. When you assemble your brake, before you fill and bleed it, make sure the lever can travel right to the bar.

Mine has now done in excess of 20,000 miles, most in tough city traffic. It gets a lot of hard use. I dissassembled it recently because the boot had ripped (it was not renewed when I did the sleeve job) and I could find no evidence of wear anywhere.

The all up price in Australia is about A$90 for sleeving, $45 piston, $49 seal kit, a total of less than  A$200. About $100US. Cheap for a good brake. If you are having problems getting your cylinder sleeved a number of people from around the world have sent their's to the person who did mine in Sydney. One bloke in the UK got his back in 18 days.The outfit which does the sleeving does many brake cylinders every day.

Partmasters 
attention Terry Milligan 
18 Harp St,  
Belmore  
NSW 2192  
Australia,  
ph 02 9787 3111

He takes the usual credit cards. I don't mind calling him for you to let him know you want to send one. 

Pistons can be made by... 

Alan Graham,  
Po Box 92,  
Douglas Park  
NSW 2569  
Australia  
(Ph 0246 32 7202)

I don't know whether Alan would want to do business worldwide. I have no financial interest in these businesses. 

Installation instructions

While soaking the seals in brake fluid inspect the piston to see there are no sharp corners that will cut the seals. Put the seals on carefully, the main trap is letting the rear one fall into the groove for the boot. It is hard to get out. I nurse the seals on with a tiny screwdriver without sharp edges.

Put the boot on the piston in the same way it goes on the original. Lubricate the cylinder with fluid and carefully insert the piston, careful with the seals. Before pushing against the spring arrange the boot and its spring clip in the right place, then push the piston down with your thumb and prod the boot and spring clip down into place with a screwdriver. It pays to start the clip by pushing one side down first so it does not get caught in the slots for the screws that hold the M/C to the switchgear.

Holding the piston down in place (don't let it pop out, the less you have to put the seals in and out of the entrance to the cylinder, the better), put the lever in and let it take the place of your thumb, and then holding the lever against the pressure of the spring, slip the bolt into the pivot. Pop a tiny amount of grease on the end of the piston and you are done...

The modification was printed in Classic Bike Mechanics Oct 1998. The article included an interesting  (and compelling) before and after comparison test as follows...


The best way to describe the end result of the modification is to talk about reduced lever pressure. It takes less lever pressure to achieve the same braking affect. The graph is a good illustration of this.

I would recommend the change to a nylon stainless braided line at the same time. If anything promotes feel it is not having what is essentially a balloon attached to your brake. The increased fluid pressure with the modification means even more balloon effect if using a rubber line.

I need to stress that the specs on this page are for a standard calliper setup only. If you have a non standard calliper with a larger piston size, or if you have a twin disc setup, the lever would need to pump more fluid to operate the brakes. The question then becomes, can it pump the fluid needed before the lever hits the bar? I'm not saying it can't be done, but you are on your own at that point. Before I proceeded with the above conversion I was worried about this as a possibility even with the standard calliper setup and had thought about shifting the primary feed hole in the reservoir to compensate if it proved to be the case.  There was plenty of room as it transpired. I was cheered by a simple measurement. The standard setup needs about 9mm of piston travel to operate the brake. Wth the square area of the piston being reduced by a factor of 1 in 3, the piston travel with a 1/2" piston would have to be about 14mm, and there was more than 20mm travel available between the primary and secondary holes in the reservoir. When you have assembled the cylinder hold it up against a handlebar and pull the lever in. Make sure there is no impediment to the lever coming right back in.

When I first did the modification I made much of the ability to lock the front wheel (do not do this at home..!) with the new brake. Subsequently I have realised I was tricking the front into locking up. If you suddenly pull the brake on you have less of the tyre on the ground than if you squeeze it slowly. 

When you squeeze it slowly you force the tyre down on the road more firmly, increasing the contact area.  I feel confident the brake will still lock the front when applied this way but either I have become more wise since the first flush or I no longer have the bottle for full speed tests. 

December 2001... I am working on a 11mm conversion. Stay tuned. Also Stan Smith of Rocky Point Cycle can create a 11mm Magura with appropriate switchgear for a Norton Commando. And RGM will now do a 1/2" conversion similar to the above for a relatively low cost by mail order. I have not seen one so cannot endorse it.

Chris Ghent
cghent@tpg.com.au

Postscript

An alternative is to send your master cylinder directly to:

Central West Brake & Clutch
PO Box 1385 
Orange NSW 2800
Ph: (02) 6362-4077

but phone ahead first

Also Justin at Halray Brake Reconditioning in Lismore NSW adds this

" I have read the article on your web site in relation to the modification of the Norton brake master cylinder. Over the years we have made a similar modification to this cylinder.It first came to my attention about 15 years ago when I was presented at my workshop front counter with a sleeve kit that a guy had purchase over the internet containing an alloy sleeve(knurled on the outside diameter), piston & seals along with instructions on how to fit. I was more than happy to utilise his piston & seals but insisted that we prepare & fit our own stainless steel sleeve. We have since produced a nmber of the sleeves,pistons & seals as required, in which we now have CNC machining facilities to produce these. Perhaps we can assist with any modifications that is needed with your club. Halray Brake Reconditioning is a business that has been sleeving since the late sixties & is recognised as one of Australia's leading sleeving & brake rebuilding companies.
Thought we may be able to assist, please feel free to contact justin@halraybrake.com.au."

Choosing Tyres for the Norton Commando

posted 25 Dec 2011, 05:02 by NOC NSW   [ updated 25 Dec 2011, 05:03 ]

Introduction

Selecting tyres for the Commando has always been tricky because of the relatively unusual 19 inch rear wheel and the transition to new and different tire size designation systems right at the time of the Commando's introduction. The trend to much smaller diameter and wider tyres on new motorcycles (which reduces the number of suitable tyres on the market) makes picking new tyres even harder.

The first thing we must do is understand how tyres are sized. Once upon a time, this was very simple. The last part of a tire size, the wheel diameter, given in inches, is still simple, thank goodness. But the rest gets complicated.

At one time, after determining your wheel diameter, one number told you all there was to know: "3.50" meant a tire three and a half inches wide. It was also three and a half inches tall, but we never really worried about that. But in the 1960s, the "low profile" concept began to affect motorcycle tyres. Those 3.50 tyres were still three and a half inches high, but the width was creeping out towards four inches. No one noticed, because the tire manufacturers didn't do anything to clue us in. With the introduction of the Commando, the low profile movement took a giant step forward, and the manufacturers took the opportunity to introduce a new sizing system to draw attention to it.

The standard big bike rear tire at the time was 4.00-18, but road racers still used 3.50-19. These were the same rolling diameter, but the slimmer carcass of the 3.50-19 ran cooler. (The biggest problem with racing tyres is usually operating temperature rather than traction- of course, traction fades as a tire overheats). In the 1960s even a hard ridden street bike could stress a good quality 4.00-18 to the point of disintegration. The lighter weight of the 3.50-19 was also advantageous- heavy wheels and tyres are flywheels and gyroscopes that make a bike hard to accelerate and maneuver.

So Norton decided to equip the new Commando with a version of Avon's 3.50-19 roadracing tire, the "GP". This was a cheap, second rate racing tire- the Dunlop KR series "Triangulars" were essential for serious racing- but the GP was miles ahead of any street legal tyres available then. At the same time or soon after, Avon decided to do something about the fact that a tire designated "3.50" was actually a little over four inches wide. Till then, tire sizes had always advanced in quarter inch steps- 3.00, 3.25, 3.50, etc. The new code used selected intermediate numbers, so the 3.50-19 racing GP became the 4.10H19 original equipment rear tire for the Commando. The 4.10 told you it was equivalent to a 3.50, but "low profile", or wider (4.10") than it was tall.

And what is that "H" replacing "-" or "x" to separate the numbers? It was the first sighting of the now familiar speed ratings, also used on automobile tyres. These were established in kilometers per hour, but those of us who think in miles per hour can regard them like so: S = 110 mph, H = 130 mph, V = 140 mph, Z = 150 mph. H is the basic rating for any sort of sporting pretensions, but if most of your riding at speeds over 110 mph is brief in duration, an S rating will do!

Shortly thereafter, a standard American sizing system starting with "M" for "motorcycle" and then using other letters to specify width, and a European system using millimeters of width, combined with a number representing the aspect ratio (that low profile business again) as a percentage, were introduced. tyres like our Avon GP are about 90% as tall as they are wide, so their aspect ratio is 90.

So a 3.50-19 equals a 4.10H19 or a 100/90H19 or an MM90H19. Today the letter designations are only used for tyres intended for Harley-Davidsons.

Now that we have our language down, so we know what we are talking about, lets look at specifics.

Front Tyres for Early Commandos

On the first incarnation of the Commando, the 1969 and 70 models, the factory equipped front tire was a 3.00-19 Avon Speedmaster Mark II. These were very skinny and very lightweight. The rubber was as sticky as you could get, but the tread was a shallow rib that faded to mere decoration as you approached serious lean angles. Availability in North America may be spotty- Avon apparently does not officially import this size anymore, but you may be able to order them from Britain or find a specialist here who imports them himself.

The Speedmaster Mark II in one size larger, 3.25S19, should be readily available. This will fit and work fine, but some slight bit of steering precision and "flickability" will be lost.

For those looking for suitable replacements in more modern tyres, the 3.00 original width translates to 80/90 in the modern metric parlance, but nobody makes such a skinny tire in 19". The 3.60 Dunlop K81 or Avon Roadrunner Universal, which replaces both 3.00 and 3.25, is an excellent choice, but, like the 3.00S19 Avon Speedmaster, neither is listed by the importer anymore, but the Dunlop at least may be sourced one way or another from Britain. A 90/90 of modern type like the Avon AM20 is a practical choice, but will be somewhat wider and heavier than the original, making the steering a bit on the heavy side.

Rear Tyres for Early Commandos and both Front and Rear for Late Commandos

In 1971 Norton introduced the practice of using identically sized (4.10H19 or 100/90H19) tyres front and rear, with the fork yokes revised to give appropriate steering geometry. Some Commandos left the factory fitted with Avon GPs at both ends, but the luckier ones wore the new Dunlop K81.

The Dunlop K81 incorporated in a street tire some of what Dunlop had learned on the track with the KR series Triangular racing tyres. It was the second tire to adopt the 4.10H19 designation, and was a world better in every way than the Avon GP. It bears two extra names, "Roadmaster", and more meaningfully, "TT100", because they were used on Malcolm Uphill's Triumph T120 Bonneville to attain the first 100mph lap of the Manx TT course by a production bike (1969 Production TT). First made in Britain of course, by the late 70s and early 80s, they were variously manufactured in Ireland, France, and the USA. Since Sumitomo, Dunlop's former Japanese subsidiary, took over Dunlop worldwide, K81s are made in Japan.

Avon answered the K81 with the Roadrunner (now known as "Roadrunner Universal") around 1973. I think it is better in all regards than the Dunlop, but not by colossal margins, and many people will argue the point. Like the K81, the only size now made for 19" wheels is 4.10 or 100/90.

Into the late 80s, manufacturers such as Metzler provided useful options in 19" rear tyres, and Dunlop's K291, K391, and K591 high performance tyres continued to be available in 19" sizes suitable for rear use. Alas, the trend to smaller wheel diameters for all road bikes has caused these to be dropped from the catalogs.

Currently most riders seeking higher performance (or better pose value) are using Avon Super Venoms or the new AM series Roadrunners. Super Venoms are the current development of the Venom introduced for the Hesketh. The Roadrunner AM series are sort of an everyday Super Venom, sharing tread patterns and general construction with the Super Venoms, but are H rated whereas Super Venoms are V rated. The original Roadrunner has been renamed the "Roadrunner Universal". It would have been a lot easier for us if they had used a different name for these completely different tyres! But they didn't, so when you go tire shopping you must keep this clear when shopping for Avons.

The AM series Avons as well as other tyres developed from the 1980s onward, are very different in basic construction from the earlier tyres designed in the 60s or 70s, and this brings up some problems with size comparison. There are always variations between actual size and nominal size and between different tire manufacturers and tire models, but the generational difference we find between tyres designed before 1975 and the more recently developed tyres makes exact comparisons almost impossible. But generally, comparing a tire of the 1980s or 90s and one of the 70s with the same nominal size, we can expect the newer tire to actually be wider and lower in profile than the older one. Due to issues of fender clearance and effect of size and weight on steering characteristics, this affects the front choices most.

For example, even though a 100/90 Avon Roadrunner Universal and an AM20 (either Roadrunner or Super Venom) share a designated size and are the same rolling diameter, the AM20, designed in the 80s, is significantly wider than the Roadrunner Universal. Logic would seem to call for the 100/90 AM series to be better described as 110/80, but not so. Why? I can only speculate that it is to indicate that it will fit the same 1.85" wide (WM2) rim as the Roadrunner Universal.

But this is why one may often want to consider a nominally smaller front tire. Continuing to refer to the Avon AM20, the 100/90 is so wide it j-u-s-t barely fits between the fender braces on a late Commando. I prefer the 90/90 AM20. It fits nicely, being exactly the same width as the 100/90 Roadrunner Universal. But it is lighter, and smaller in diameter, and thus provides really sharp, nimble steering.

Further complicating the issue for the Commando rider wanting a set of AM series Avons is the fact that 19" Super Venoms are available only in 100/90V19 (AM20 front or AM18 front or rear). The AM20 front tread is made as a Roadrunner in 90/90H19 and 100/90H19. The Roadrunner rear tread, AM21, is not available in 19" at all.

All Avons are still made in Britain, a factor which prejudices some of us with British motorcycles in their favor.

Another option, although the idea will upset by-the-book types, is to select a 19" tire designed for front use that looks stout enough to handle the guff, reverse the direction of rotation, and mount it on the rear.

For example, the Michelin Tarmac, sold as a "high performance cruiser tire", is made for front use in 90/90H19 and 100/90H19. The adventurous early Commando rider might try those sizes front and rear respectively, and riders of late Commandos could try 100/90 at both ends. No guarantees, especially of rear mileage.

And at this point, we should remind ourselves that there is no such thing as good mileage on a 19" Commando rear tire!

Then there are Cheng Shins... made in Taiwan, cheap, lousy wear, but recommended by some as giving good value for money. Their C199H is a copy of the Dunlop K81.

Suggested Tyres

To sum up, my suggestions, for 1969-70 Commandos first:

Concours display:
Front: Avon 3.00S19 Speedmaster Mark II
Rear: Avon 3.50H19 GP (Current manufacture in race compound reverts to "plain" inch sizing.)

All around riding:
Front: Dunlop 3.60H19 K81 or Avon 90/90H19 Roadrunner Universal, if you can find either one.
Rear: Dunlop 4.10H19 K81 or Avon 100/90H19 Roadrunner Universal

Very fast riding:
Front: Avon 90/90H19 Roadrunner AM20
Rear: Avon 100/90H19 Super Venom AM18

For 1971-75 Commandos:

Concours display:
Front and Rear: Dunlop 4.10H19 K81 (New old stock if possible- Made in England is best!)

All around riding:
Front and Rear: Avon 100/90H19 Roadrunner Universal

Very fast riding:
Front: Avon 90/90H19 Roadrunner AM20
Rear: Avon 100/90H19 Super Venom AM18

The 18 Inch Rear Wheel

Converting the Commando rear wheel to 18" diameter has been seen as a panacea for the limited choice of 19" tyres. Fifteen years ago, when the 18" rear wheel was still the industry standard, this would indeed expand your choices to include state of the art rubber. Today, as the industry standard moves toward ultra wide (three and a half to six inches or more) rims of 16" (cruisers) or 17" (sport bikes) diameter, the latest high tech radials are not going to be available in any size useful to us. But you will still find a wide range of 4.25/85 or 110/90H18 rear tyres, so many that I won't even attempt to chart them all, except to say that I am partial to the Avon 110/90H18 AM21 Roadrunner.

The conversion can be done without much difficulty. For street use a WM3 rim, 2.15" wide, would normally be used, although racers will want the widest rim allowed for their class of competition. New rims are available from many sources. The premier American supplier of spokes, Buchanan's, will provide a set of stainless spokes and nipples for about $80. A rim and spokes for a Norton Atlas would fit perfectly, of course.

Many bikes have similar spoke patterns, and any 40 spoke wheel with the same spoke flange diameter as a Norton rear hub is a potential source of rim and spokes. I built my first 18" wheel for my Commando with a Borrani aluminum rim intended for a drum brake Moto-Guzzi and an aftermarket spoke set for a Kawasaki Z-1.

But do not think you will make your Commando handle better with an 18" rear wheel. You may think it will provide more traction, but traction is not handling, and a stock Commando has no need for more traction. What a bigger contact patch does provide is a bigger area over which to dissipate traction's enemy, heat (obviously the tire engineers have long since overcome the limitations that caused Norton to select the 3.50-19 rear tire originally), and that is truly advantageous- when you are pumping 100 horsepower through the tire to maintain 130 mph on the banking at Daytona.

Otherwise, the larger tire merely adds weight- increasing the flywheel and gyroscopic effects that make a bike feel comparatively unresponsive. Not that a 110/90H18 rear tire will by itself transform your Commando into a leaden, unturnable cruiser. Rather it will show just a bit more stability and less responsiveness to throttle or steering inputs. But this is not usually the kind of handling we are looking for from a motorcycle like the Commando.

In the case of a Commando built for racing, handling response may have to be sacrificed for sheer grip, and the choice and ready availability of 18" race tyres make an undeniable argument for converting. The poseur who requires that his bike look fast may find a compelling need also!

On the street, the 18" tire can usefully improve load capacity and especially wear. A 100/90 tire is typically rated in the high 400 lbs of load carrying capacity, whereas a 110/90 will be 10 to 15% more, in the mid 500 lb range. And the best 100/90H19 rear tyres last no more than 3,500 miles under most circumstances, while a 110/90H18 can take you right past the 5,000 mile mark. For these reasons, the touring rider, especially if of large size himself, or who commonly rides two up and heavily laden, may well give serious consideration to building an 18" wheel for his Commando.

But most of us, with our mix of occasional commuting to work, Sunday morning sport rides, and hauling a sleeping bag a few hundred miles to a weekend rally, are best off with the standard 19" rear wheel.

(Availability of tyres specified in this article may differ outside the US)

by Ben English

Spoked Motorcycle Wheel Building

posted 25 Dec 2011, 05:00 by NOC NSW   [ updated 25 Dec 2011, 05:01 ]

The Wheel

Before doing any wheelwork, note the position of the rim in relation to the hub. Look at your bike with the wheels still on the bike. Check maker's specifications if you have them. Note which way around the wheels and hubs are in relation to the bike. Mark the rims and hubs so you will know which is the left side and which is the right side. Some wheels are asymmetrical, but it is still good to fit them back on the way they came off. There maybe some other unforeseen reason why at a later date you wish you knew which way the wheels originally were. Take notes, draw pictures, take photos. It may be weeks, months or years before you get it all back together. Measure the offset of the rim to various bits on your bike. Swing arm, forks, shocks etc. Make notes. You can use this information to double check everything after final assembly. Take the wheels off the bike and measure rim offset in relation to the hub. Use a straight edge across the rim to measure to the datum on the hub or a straight edge across the hub to measure to the rim. Draw pictures of spoke patterns. Use a datum point like the face on the hub that the disc or sprocket sits against. If the hub is a brake drum hub, then use the edge of the brake drum opening. Take notes on how the wheel appears before you pull it apart. Note what you used for a datum surface. Match mark the parts as you disassemble them. Small centre punch marks are unnoticeable to anyone else but you. Make notes or drawings of where you match marked the parts. Draw colour schemes or pin striping details. This sort of preparation and detail will save you a lot of headaches later on.

The Hub

Wire spoked wheels have a metal hub with wire spokes passing through holes either directly in the hub or flanges on the hub then running outwards radially or tangentially to the rim where they pass through holes drilled into the rim. Some hubs may not have flanges. Like the later Matchless or BMW. These hubs are drilled to allow straight pull spokes to go straight through the extreme ends of the hub. Flanges can be out at something like 45 degrees to the axle like on some Harley Davidson's and trail bikes or the flanges can be at right angles to the axle as on most bicycles and motorcycles. However no matter what the attaching point on the hub, the spokes must be made with a head angle and head length to suit that particular hub/flange design.

Rims

Rims are usually a flat steel or aluminum strip rolled into shape with the ends butt welded together. Basically this flat strip has flanges rolled up on each side to keep the tyre on and a valley around the centre to give strength and rigidity to the rim and help ease the tyre onto and off the rim at tyre change time. The depth of this valley makes a huge difference to the ease of tyre changing. The deeper the valley, the easier it is to change a tyre. The cross sectional shape, made up of the rim flanges, the rim and the valley all work together to give the rim strength. Inside the rim should be clean and free from rust and corrosion. This should be checked and cleaned every tyre change. There should be a rubber rim band fitted in the valley covering the nipples to give protection to the tube. The quality of the rim is in the material used and the roundness, trueness and welding. Some poorer quality rims have a very obvious weld and a definite flat spot right on the weld where they haven't been properly re-rolled. A pain when it comes to truing up the wheel. Rims can be bought in various materials such as unpainted steel, chromed steel, aluminum alloy and stainless steel. Flat spots, buckles and twists may be able to be pulled out of bicycle rims by pulling with spoke tension however motorcycle rims are very much stronger and it's been my experience that trying to do this on a motorcycle rim is generally a waste of time. It may be possible to move the rim a small amount, but the payoff is over tensioning of some of the spokes, which results in uneven load sharing by other spokes causing spokes to continually come loose or break. Take the wheel apart and get the rim re-rolled or simply replace the rim.

The rim valleys have dimples pressed into them for every spoke. On most wheels the dimples are offset off the centre line of the rim, half to one side, the other half to the other side. The dimples are equally spaced apart around the rim. The dimples are to recess the nipple and give a hemispherical surface so spoke holes can be drilled at the correct spoke angle to suit the hub. If these holes are not drilled at the correct angle, you will notice the spokes will be bowed when the wheel is assembled and tightened. These spokes will break in service. Make sure the hole angles are correct! Some rims have the spokes going to the hub flanges from holes drilled on the same side of the rim, some rims have the spokes going to the hub flanges from holes drilled on opposite sides of the rim. That is, from left side of rim to left hub flange, right side of rim to right hub flange. While others go from left side of rim to right hub flange, right side of rim to left hub flange. An example of the latter is the disc brake wheel on the front of a Norton Commando. All should be revealed on proper examination of the bits. If in doubt, look for maker's specs or look at other similar makes of bike.

Rim orientation

If you are building a wheel from scratch, you will have to lay the rim down on a bench and have a good look at it. The holes around the rim are drilled slightly offset to the centreline of the rim and should be drilled on such an angle so when fitted, the spoke will look directly at it's correct hole location in the hub flange.

Check that you have the rim the right way around to suit your hub. For asymmetrical hubs like Triumph conical hubs or hubs such as the front disc brake wheel on a Norton Commando that have a dramatic offset, you can get a good idea of which side of the rim will go to which side of the hub, by putting a couple of nipples through a couple of spoke holes, screwing spokes into them and holding the nipples firmly in the rim holes with finger pressure. The spokes will stick out at whatever angle the holes were drilled. You should be able to get an idea of hub flange position if the holes in the rim have been drilled at the correct angle, this should be indicated by the direction of the spoke and it should become obvious which way the rim should face for the spokes to connect up with the hub flanges when all is in the correct place.

You now need to look at the spoke holes adjacent to the valve hole. Basically, with the rim lying flat on a bench, valve hole to the top, every second hole should look up and every other hole should look down. Look at the two holes immediately each side of the valve hole and note which hole looks up and which hole looks down. Rims can be drilled either way, with the hole to the left or right of the valve hole being the hole that looks up. At the moment you are only interested in the hole that looks up. This will be your starting point for lacing the wheel. Remember this hole. You will need it later.

Spokes

Spokes have a head on one end to stop them from being pulled through the hole in the hub flange and an adjustable threaded nipple on the other end that goes through the hole in the rim. Spokes can be straight pull-spokes such as on some BMW's and Matchless or the spokes will have a bend at the head so the spoke can go at an angle through the hub flange. The spokes need to have a head length to suit the hub flange thickness. They also could have a different head length depending if they are inside the flange or if they are outside the flange. The outside flange spokes have a longer distance to reach around to bring them into line with their corresponding rim hole. This means that for a symmetrical hub/rim assembly that has same diameter left and right hub flanges, there will be two different groups of spokes. One lot of spokes dimensioned for inside the flange, and one lot of spokes dimensioned for outside the flange. The inside spokes may be shorter overall and have a shorter head length and an obtuse head angle, while the outside spokes may be longer overall and have a longer head length and a more acute head angle. If there is an offset between hub and rim, or the hub has unequal flange diameters, there will be a difference again between left and right inner and outer spokes. So there is a possibility that there could be four different spoke types for a particular wheel. Sometimes three different types, but mostly at least two different types. Be aware of this and make sure you have all the right spokes for the right wheel. Make sure you are familiar with which spokes go where at the time of lacing the wheel. Don't take it for granted that the spokes you have are the correct spokes.

Check your spokes against maker's specs if you can. Check your new spokes against the old ones if you are rebuilding a wheel with new spokes. Lay all the spokes out and put them into like groups. In a 40 hole rim there will always be look-alike groups of ten or multiples of ten. Compare, compare, compare. For example the Commando front disc wheel has ten outer left spokes, ten inner left spokes and twenty right hand spokes. Each group should be similar. You won't have 9 in one group and 11 in another, look again.

Spokes are usually cad plated steel. Stainless steel is a popular shiny material favoured by many for looks. Some people like to chrome spokes. Chroming can make the spoke material brittle. This is not such a good idea as spokes will 'work' in use and anything that works can suffer fatigue resulting in spoke breakage. Brittle spokes will not be as resistant to fatigue as standard spokes. The spoke nipple usually has a square on the shank to enable adjustment with a spoke wrench and a slot in the head for a screwdriver for faster running up or down. Sometimes the nipples have a dished washer under them. The threads on spokes are not normally cut with a die, but rolled into the spoke.

This is a more reliable method of thread creation on an item that is liable to suffer from fatigue. Rolling the threads into the material doesn't cut across the grain structures, but rolls the threads into the grain structure and is a stronger method of thread manufacture, it has less chance of developing a fatigue concentration point along the thread. The minor diameter of the thread on the spoke shank is the thinnest part of the spoke and the weakest link in the chain. Spokes will break at this point. Spokes will also break on the bend at the spoke head where the spoke goes through the hub flange. Some hub flanges have countersunk holes. This is not for the spoke head to sit in, like a counter sunk screw, but for the bend at the spoke head to sit in. If the bend sits against a square unchamfered edge of a drilled hole, the sharp square edge will work against the spoke and create a nick or fatigue point, which is usually where the spoke will break.

However, many wheels have only countersunk holes on the outside of the flanges. This is probably because the outside spokes have the sharpest bends in them, the spoke bend sitting hard in against the relief given by the hub flange hole countersinkings. The inner spokes, because of their direction inward toward the rim, start to leave the side of the hub flange hole as soon as the spoke exits the hole. Spokes can be the same thickness along their full length or they can be waisted toward the head end. Spokes are described in the following way as is in the factory Norton Commando manual. Rear outer: 6.093 in long: 8/10 SWG: 90 degree head: offset length .531 in. This gives the length of the spoke, the gauge at the narrow end and the gauge at the waisted end, spoke head angle and spoke head length.

Tensioning a spoke is usually done by feel or by ear. Typically a wheel is tuned like a piano, meaning the spokes are struck gently with another metal object like the spoke wrench, listening for the pitch or note given by the spoke. The spoke should have a nice "ding" sound, not a dull "thud" or sharp "ping". A spoke that touches another spoke will not ring clearly, by bearing a light weight on the other spoke you can get it out of the way in order to listen to the "ping". There are torque figures and spoke torque wrenches, but these are not often used. It is easy to get false readings on the torque wrench unless all the spoke nipples are in excellent order. The slightest sticking of a nipple could give a false reading. The best, quickest and most accurate method is the tuning method. Just to give an idea, the torque figure listed in a Honda Gold Wing manual for spoke adjustment is 17-38 in/lbs (2 - 4.5 Nm) The spoke and nipple threads should be coated in an anti seize compound to help with tensioning and later adjustment or disassembly. The threaded end of the spoke gets all the weather, goes through all the puddles and needs lots of looking after. Be careful tensioning spokes on a brake drum. Over tensioning can pull the drum out of round. Check the drum for trueness after you have finished building the wheel.

Only cut out the old spokes if the nipples are frozen solid. Pulling the spokes out will give the first timer a chance to get familiar with the spoke pattern. Also gives some time to look over everything and put some thought into the job. If the spokes are in reasonable condition, they can be used again. If replacing the spokes with new ones, the old ones can always be kept as spares. If you know they are the right spokes as per maker's specs, then they should be kept as samples. The new ones you get may not be right! Don't destroy things unless you have too. Mixing spokes of different gauge can give problems in tensioning and load sharing. Thicker spokes will share the load easier than thinner ones. Loose or broken spokes may result in this practice.

There are several different methods or patterns of spoking that can be used on spoked wheels. E.g., Radial, Crows Foot and Cross or Tangential spoking. Most motorcycle wheels use the Cross or Tangential pattern of spoking, where pairs of spokes form a series of crosses around each side of the wheel. In this pattern the spokes come on a tangent from the hub to the rim. This pattern is stronger and much more rigid than the other two patterns and is able to transmit torque which is the forces of power delivery and braking from the hub to the rim/tyre/road much more effectively without danger of the hub twisting out of the spokes/rim. It is also better able to transmit the impact forces of the wheel striking bumps in the road, back to the suspension. The loads are carried through a larger number of spokes than the other patterns.

Wheels with the Cross or Tangential spoke pattern will always have an even number of spokes. For example, most British wheels use 40 spokes. They use the Tangential pattern of spoking. Japanese maker's also use the Tangential pattern, but mostly choose to use 36 spokes. Once again, an even number. Crows Foot pattern uses a combination of Tangential spoking and Radial spoking. The cross pattern is used, but there is one radial spoke going straight from hub to rim, right through the middle of the cross. This pattern uses groups of three spokes and so will have an odd number of holes around rim and hub. If you find a rim at a swap meet with an odd number of holes, this is most likely why. So check the number of holes in your rim.

Dimples are pressed around the valley of the rim equal distances apart, but every second hole will be off centre to one side, the other holes will be off centre to the other side of the rim. To drill the holes in the dimples for the spokes the correct angle must be used. It is very important that this angle is calculated and drilled correctly because it will determine if the nipple will sit true and straight and be absolutely in line with it's corresponding hole in the hub flange when all is together and tightened up. These holes will not necessarily have the same angles for left and right side of the wheel as the hub may not be central inside the rim, or the hub may have different diameter flanges as is the case with Triumph conical hubs and most early hubs that did not have a full width brake drum. So it's very important to have a rim with the spoke holes drilled at the correct angle and it is very important to know which way around the rim goes in relation to the hub so the right spoke angles match up with the corresponding hub flange diameter.

Lacing up a Wheel

Step One:

Place the hub on a bench top in front of you or hold the hub in one hand flanges horizontal. Remembering that you could have four different sets of spokes, decide which spokes are for INSIDE the top flange as the hub appears in front of you. Holding the correct spokes in the other hand, start sticking a spoke down every other hole around the top flange. These spokes will be inside spokes.

IMPORTANT BIT: Now is when you check which holes lead and which holes follow. Still with the hub in front of you the same as when you started. Do not turn it over. Look straight down over the hub. Look straight vertically past a spoke hole on the top flange that you have just put a spoke into. Looking down onto the bottom flange, you will notice the holes in the bottom flange are not directly under the holes in the top flange. They are midway between them. Now remember back to when you looked at the holes in the rim each side of the valve. If your rim had the looking up spoke hole to the left of the valve hole in the rim, go to the next hole in the bottom hub flange immediately counter clockwise back from a hole in the top flange that you have just put a spoke into and with the correct spokes for OUTSIDE the bottom flange, start here and stick a spoke through every other hole around the bottom flange. OR if your rim had the looking up spoke hole to the right of the valve hole in the rim, go to the next hole in the bottom hub flange immediately clockwise back from a hole in the top flange that you have just put a spoke into and with the correct spokes for OUTSIDE the bottom flange, start here and stick a spoke through every other hole around the bottom flange. This bit can be quite tricky if you have hub flanges of very different diameters. You may have to go over it a couple of times to make sure you have the spokes in the correct holes. Now you should still have the hub in front of you with flanges still horizontal and twenty or so spokes hanging straight down.

Step two:

Still with the hub in front of you the same as when you started, sweep all the spokes back around both flanges so they are in two bundles (top and bottom) Hold them so they don't fall out and turn the hub over. Repeat step one with the rest of the spokes, making sure you have the correct spokes in the correct flanges. Go around the top flange first, sticking the INSIDE spokes down through the flange from the outside, then around the bottom flange, sticking the OUTSIDE spokes down through the bottom flange from the inside, ending up in the correct direction (inner or outer) phew! Now you should have a hub with 40 or so spokes in it. Looking down onto the hub you should have every other hole alternating between a spoke head and a spoke shaft on each side of both hub flanges.

Step Three:

With the hub laying on a bench top and all spokes extended outwards radially, sweep all the spokes around so they are bundled together in one spot. Place the wheel rim over the hub, roughly in it's position valve hole to the top or furthest away from you. If your reusing your old rim, lay the rim over the hub keeping the same direction of rotation as it was before you pulled the wheel apart. Look up your notes, drawings and photos if you have to. If it's a new wheel build, make sure the rim is around the right way for the spoke angles in the rim holes matching up to whatever hub you have. Offset or unequal hub flange diameters. (You can establish this by checking spoke angles as per the rim orientation paragraph above.) Take any head up spoke from the top flange (spoke head up means the spoke head is facing upwards, with the spoke inside the flange) and put it in the first looking up hole adjacent to the valve hole. Remember, you established this earlier on, so you should be right now!! Use anti seize on the threads. Thread a nipple only four turns on each spoke as you lace it into the rim.

Step Four:

Count off five spoke holes to the right, including the hole you spoked in step three. This must also be a looking up hole. Into this put the next head up spoke to the right of the one you spoked in step three. Continue this sequence until you have laced up all the head-up (inside) spokes in the top hub flange. The wheel will now have ten spokes in holes with three spoke holes between each spoke. The centre of the three empty holes will be a looking up hole, the other two, looking down holes.

Step Five:

This is a critical step, so take it slowly and repeat it if you don't get it at first. Take the partially spoked rim and hub, and, keeping the same side up, rotate the rim so the spokes are at an acute angle. Because of the spoke angles drilled in the rim, it will be immediately obvious if you go in the wrong direction. Depending on how the rim has been drilled (angle of the holes in the rim) rotate the rim left or right. Hold the hub as you rotate the rim.

Step Six:

Another critical step. Take any head down (outside) spoke from the top hub flange (The wheel should not have been turned over!!!) and going in the opposite direction from the spokes laced so far, cross over the top of the other spokes and stick it in the remaining looking up hole. Thread a nipple on it four turns. This spoke should have gone into the middle remaining hole. Continue lacing all the head down (outside) spokes in the top flange. When you are finished there will be twenty spokes in groups of twos.

Step Seven:

This is a most critical step. Turn the wheel over. Now, all the unlaced spokes will be in the top flange. Straighten spokes out and sweep them all out of the way. Things should look like they will now fall into place as these remaining spokes will only go into their rightful holes. Start with the head up (inside spokes) spokes on the now top hub flange. They will only go into one set of holes. Stick them in their holes and thread their nipples on four turns. Next do all the head down spokes crossing them over the outside of the spokes you have already laced and thread their nipples on four turns. While motorcycle spokes cross other spokes one, two or three times, they shouldn't weave in and out of one another like on bicycles. Bicycles spokes are much longer and thinner.

How to True a wheel

Step One:

Put your wheel into your jig. Your jig can be a pretty flash purpose made professional expensive things or can be a simple homemade stand. Something like an old swing arm clamped vertically in a vice will do. You don't need to use the wheel's own axle if it doesn't fit the jig. Any round bar that fits will do. The wheel rotates on the bearings, not the axle. It is handy to have some spacers each side of the wheel to stop it moving side to side while tightening or loosening spokes. Nuts and washers will do. You will need some form of pointer to check radial and axial runout. A black felt tipped pen is a good idea as well. Use a dial gauge only to check your final alignment. Get a comfy stool like a bar stool and sit it in front of the jig, have a cuppa handy and start work.

Step Two:

Using a screwdriver and starting at the valve hole go around the wheel and screw all the nipples down so the last spoke thread just disappears under the nipple and stop. Adjust radial runout first. Side to side wobble comes last. Once the wheel is more or less within 6mm or so radial runout, start on sideways runout. Get this down to about 6mm as well. Check radial again. Don't tighten the spokes!

Step Three:

Now we must look at rim off set. You'll find that if the spokes are original parts, or they have been correctly made by aftermarket people, the rim should have come somewhere near it's correct position. Go back to your notes or manufacturers specifications and see what the rim offset should be. Using the same method of measuring as you did before you stripped the wheel measure the offset of the rim as it is now and make a decision on which way it should go to be correct. Now tighten up whichever side spokes need tightening to move the rim in the desired direction. Don't do any spokes up too tight. Move your rim into position with the spokes not very much more than finger tight. Once the rim is in it's correct position, get out the felt pen and true the rim again. Holding the pen firmly against your jig, rotate the wheel and move the pen tip toward the rim. As the rim rotates the runout will contact the tip leaving a long black mark around the rim. This gives a clear indication of which way and where the rim needs to be adjusted. Adjust the spokes, wipe off the black mark and do it again. Check offset, check radial runout, then check axil runout

Do this enough times until you are happy with your work, then gradually go around tightening the spokes. They don't need to be death tight. There are lots of them and they all need to share the work equally. As you rotate the wheel strike the spokes lightly with you spanner. They should start to give a nice crisp 'ding' not a dull 'thud' or an over tightened 'ping'. Get a soft-faced mallet and go around the wheel and give every spoke a light wack. This will settle the spokes, one might have been tightened up with a slight bow in it. A gentle knock with the hammer will spring it into line and it will now probably have a dull thud to it when struck with your tuning spanner. By now the wheel should be pretty close to being right. Keep checking offset, checking radial runout, and checking axil runout

Time for a cuppa or a beer. Come back later after the nerves have settled, run around it with the tuning spanner, ding, ding, dong, ding and give it that final touch……….. Should be pretty right after all that.

Finishing

If your keen enough, you can now check your work with a dial gauge. Most motorcycle manuals specify a maximum runout figure of 2mm or .080 in. You should easily get a new rim well under 1mm or .040 in. An old re-laced rim would still come somewhere near 1 mm or .040 in unless it had a bit of a woof in it. Put the rim band on, fit your tyre and make sure the bead sits down properly and you have correct air pressure. Put the fully assembled wheel back up in your jig and give it a slow spin and see how it goes for balance. Static balancing a wheel is another easy job that makes a lot of difference to the performance of the bike. You can buy proper wheel weights that either stick onto the rim or clamp around the spoke. You can cut strips of lead and wrap them around the spokes or cut strips of lead and stick them to the rim with silicon.

Spin the wheel slowly and wait for it to come to rest. Mark the top of the tyre with chalk. Spin the wheel slowly again and see if it stops in the same place. Add some lead weight to the top of the wheel by wrapping it around a spoke or by taping it to the rim. Spin the wheel again. Repeat this and add or subtract weights until the wheel takes a long time to stop turning and will stop in any position. Fix the lead weights properly to the rim. If you wrap strips of lead around the spokes, wrap electricians tape or similar around the windings. Stick the strips to the rims with silicon and tape over the weights until the silicon has set. Fit wheel to bike.

All there is to it really………….

Revs and Speed Calculator

posted 25 Dec 2011, 04:54 by NOC NSW   [ updated 25 Dec 2011, 04:56 ]

Download a revs calculator speadsheet. Enter your own values.

Norton Roadholders - The Hole Story by Peter Crespin

posted 25 Dec 2011, 04:51 by NOC NSW   [ updated 7 Dec 2012, 16:03 ]

Commando Forks are known to be inadequate by modern standards. There are many modifications ranging from using different grades or amounts of oil to buying reworked Showa internals from Kenny Dreer. The following is a telling of what has come to be known as the Covenant Conversion.

Most of the British Motorcycle manufacturers of the classic era deserved their reputations for producing well designed and solidly-built machines. Yet even the proudest names occasionally produced designs which became famous for their faults rather than their finer points. Triumph fans prefer not to talk about the sprung hub and Norton devotees change the subject when you mention Commando Combat engines. Royal Enfield buffs admit that the Crusader five-speed gearbox was "Made like a gun" only in that it regularly exploded with a bang. BSA, Velocette and others all made the occasional blunder. As the saying goes: "A man who never made a mistake never made anything." In fact it is this fallibility that attracts many people to these older machines today. There is often the real chance of actually improving in old design with today's materials and technology. If such modifications are done sensitively, only the most fussy of concours types can object. For those of us who actually ride our machines regularly, modern paints, electrics, tyres and so on are welcome developments. This article describes a couple of simple modifications to the later of the two Norton Roadholder fork designs. These mods improve the forks' damping characteristics, without affecting the appearance of the machine. 

The original Roadholder design, itself a development of a pre-war non hydraulic version, was launched In September 1946 for the following season. It used a double-taper damper rod which passed through a restrictor inside the bottom fork bush. The design worked well enough at the extremes of travel as the taper took effect, but the damping provided around mid-travel was limited to moving oil in or out of the space between the upper and lower fork bushes. This was the so-called Long Roadholder.

The later Short Roadholder fork was fitted to Featherbed-framed models from 1953 onwards. It was to continue largely unchanged until Norton ceased manufacturing in the mid-Seventies. It also appeared on some of the hybrid AJS and Matchless machines made in the final years of the Associated Motorcycles (AMC) empire.

For normal road use, this later design was a distinct improvement and closely followed the pattern of the Matchless Teledraulic fork. The fork now used a separate internal damper tube and shuttle valve arrangement which gave more precise control over the middle portion of fork travel. It is easily distinguished from the earlier design by the lack of an external spring and the presence of a damper rod screwed to the underside of the fork top nut. Unfortunately, it was at this stage that two design flaws, not present in the original Matchless fork, crept in. As the faults only affect damping near the extremes of fork travel, it is perhaps understandable that no mention of any deterioration was made in the road test reports of the day. Doubtless, if riders of the brand new Featherbed machine, introduced in 1953, had gone for a quick blast round the local slag heap, some of them would have noticed that all was not well with their forks. More specifically" the new design lacked proper hydraulic bump stops to cushion the final metal-to-metal contact at the two extremes of front suspension movement. The other Roadholder features which made it such a good example of its type in the Fifties, were still there: the large-diameter stiff fork stanchions, the solid fork yokes and the light alloy sliders. The bumpstops, however, had effectively disappeared.

Most, if not all, motorcycle forks with hydraulic damping incorporate some arrangement for minimizing noise and uncomfortable metal-to-metal clashing at the extremes of travel. Car designers, with their concealed suspension systems, usually resort to crude but effective rubber bump stops. These are normally tapered, to give a progressively firm control as the suspension nears the limit of its movement. In motorcycle design, where appearances have to be taken into account, this simple solution is not often employed except on spring/damper units, where a rubber collar is often fitted round the damper rod as a bump stop for the rear suspension. As an aside, many enterprising riders in the heyday of the cafe racer seemed to use this system on their front suspension (or a fibreglass-in compression variant), judging by the number of badly-fitted and tyre-marked fairings around in those days!

The more conventional methods used by telescopic fork makers almost always involve either a tapered, moving restrictor arrangement or a progressively blanked-off hole system. By such methods the damping over the last inch or so of travel is rapidly increased, in order to avoid metallic contact between sprung and unsprung components. Those of us reared on old British field bikes will remember the sickening crash of slider on stanchion, audible at a hundred yards, as we launched our tired steeds off yet another death-defying molehill. In our youthful exuberance, we took these jolts as a matter of course and marveled all the more at Messrs Smith, Eastwood, Bickers et al. Little did we know that two-bob's worth of oil and new oil seals would have made the old banger float like a butterfly!

Getting back to Roadholders, the Norton designers tried to include both of the above methods, viz a blanked-off pair of holes (one large then one small, in sequence) at full extension, and a tapered restrictor on full compression. Sadly, unlike the Matchless version, neither arrangement works properly.

A quick glance at the illustration shows that as the slider moves down the stanchion, the oil trapped in the space between the top and bottom bushes is squeezed out through the large upper holes and the smaller lower holes. This provides some damping to supplement the effect of the separate damper assembly. In theory, as the slider nears the end of its travel, first the large holes and then the small holes are blanked off as they disappear inside the top fork bush. This leaves a small cushion of oil trapped between the two bushes to stop them hitting each other and putting excess strain on the materials (and your eardrums). As far as it goes, this design is perfectly sound. Unfortunately, it literally doesn't go far enough. Unlike the Matchless, Triumph and countless, other designs, the large and small oil passages are not actually blanked off at all; this is because the slider never moves far enough down the stanchion for the top bush to cover them. What happens is that the delicate damper valve assembly strikes the underside of the damper tube top at a point where the stanchion oil-holes are still about an inch below the top bush. In practice, therefore, instead of a nice oil cushion providing a proper bump stop, the damper valve has the job of limiting fork extension when it suddenly hits solid metal - a job it should never really be expected to do.

If those of you with Roadholders don't believe me, remove the fork top nut from one side of your forks, (having first taken off your front wheel and mudguard) and fully extend the fork leg. You will notice that the damper rod disappears an inch or so below the end of the stanchion. In other words, when the top nut is in place, it and the attached damper rod stop the forks from extending as far as they otherwise would. For those doubting Thomases who are still unconvinced, have a look at the underside of the damper tube top and you'll see the tell-tale marks in the alloy where it has been struck by the damper valve.

You may have noticed during the earlier procedure that the last bit of fork extension happened only slowly, no matter how hard you tried pulling the slider down (assuming you have some oil in the fork leg). This was because the hydraulic 'lock" - ie the bump stop - was working for a change, since the damper tube no longer limits fork travel when you take the top nut off. In a moment you will learn, if you haven't already guessed, how to get that bump stop working properly with the fork fully assembled.

Meanwhile, what about the other bump stop, the one supposed to work at the point of full compression? Well again the Norton designers missed the chance to design a proper system. In fact if, as seems likely, they more or less copied the Matchless design, their copy was not as good as the original. From the illustration you can see that as the slider rises on the fork, the base of the stanchion and its bottom bush act like a piston, forcing the oil up between the stanchion and the damper tube. As the forks near full compression, however, the base of the damper tube (which is tapered) progressively restricts this escape of oil. The widest part of the tapered section almost completely blocks the passage of oil up the inside of the fork stanchion. The oil is therefore trapped and forms an hydraulic cushion that prevents bottoming out under normal circumstances. Or rather it should do, but again the Roadholder idol turns, out to have feet of clay.

In this case, the design is flawed because there are holes drilled on or under the taper section of the damper tube, rendering the desired hydraulic lock impossible. Naturally, some sort of hole is required in the damper tube to allow oil to flow in behind the damper valve, as it travels up the tube during fork extension. The Matchless design, amongst others, puts this hole (or holes) near the base of the damper tube but just above the taper. In this way the oil can enter the damper tube freely during extension, but when the fork nears full compression the oil has nowhere to escape from below the taper, so the proper cushioning effect is available.

At first, the Norton people put four 1/4 in. holes in the plain section at the very bottom of the damper tube below the tapered part. With four such holes the oil is never really compressed below the taper on full bump, it simply flows away up the damper tube past the open shuttle valve. Since no hydraulic lock can possibly occur, the forks may bottom out on rough surfaces.

By the time the Commando appeared, the Norton designers had hashed the hole (sic) idea, so that now there were two holes instead of four and they were drilled through the flanks of the taper itself rather than below it. In as much as this modification allows the very last part of the fork travel to form an hydraulic lock, it represents an improvement over their first attempt. However, in so far as it represents a repeat of the earlier mistake, albeit in a less spectacular fashion, it really is rather daft.

It does not take a degree in mechanical engineering to work out that there may as well be no taper at all above the lowest edge of the holes. This is because, as before, there is no real restriction of oil movement during fork compression, since it just squirts up inside the damper tube through the holes. Only when the bottom of the stanchion passes beyond the lower edge of the holes, does the taper cause any restriction and thereby provide a belated cushioning effect. Now you know why Norton never used an offset spindle like Velocette and Royal Enfield did - they had to keep the spindle under the bottom of the fork leg to stop the stanchions poking through when twin leading-shoe brakes were invented (don't laugh, it might be true!).

Still, despite everything I’ve said so far, most people seem more or less content with their Short Roadholders as they are. Certainly they give a reasonable ride - commendably free of fork flex - over average road surfaces. Nevertheless, by means of a couple of simple modifications, their behavior on poor surfaces can be transformed. As some of our roads begin to resemble the rolled and graded scrambles tracks of yesteryear, the modifications will be of benefit to almost any machine fitted with these forks.

To provide a proper bump stop on full extension, it is only necessary to arrange for the holes already in the stanchion near the bottom bush, to be blanked off in sequence. At first sight, the easiest way might seem to be to make up a longer damper rod to allow the forks to extend fully. However, even if the fork springs were packed up to provide the extra extension required such an arrangement would not be desirable because of the limited overlap, or engagement, of slider over stanchion. To maintain adequate stiffness of the front forks, there should be several inches of stanchion inside the slider even on full extension.

The best way of providing a bump stop in this design is simply to make longer top bushes - about one and a half inches longer in fact. The exact length is adjusted so that even when completely extended, with top and bottom bushes in contact, the damper valve stays just clear of the underside of the damper tube top. With such bushes fitted and the fork topped up with oil, the last fraction of travel is properly cushioned as the oil holes are blanked off in turn until the hydraulic lock occurs. The effect is immediately obvious if the engine is out of the bike, since even under such circumstances (when the rolling chassis on its own is seriously oversprung) it is impossible to top out the forks. If making special fork bushes is not possible, then the insertion of a collar under the original fork bush is a reasonable compromise.
Again, the extra collar should be about one and a half inches long, with the final adjustment best made by measuring up the various fork components to see -how far below the top bush the stanchion oil holes are kept by the damper assembly at full extension. Unlike an extra-long top bush, the collar will need to be prevented from falling down inside the slider and the best way of doing this is to make it a snug fit in the top of the slider and a looser fit over the stanchion. In this way the collar can be tapped down into place as the top bush is fitted. A drop of Loctite Bearing Fit could be smeared on the outer diameter if there is any suspicion of looseness further down inside the slider.

Triumph used a separate bush like this (made of a plastic material) in the forks they manufactured between 1964 and 1971. With the Roadholders it is possible to use an old fork top bush if you can't get a spacer made up. A slightly worn bush is probably best, as there is less chance of it being pulled down the slider by the stanchion. Trim the brim from the top hat shape and ensure the bush is a firm fit in the slider don't forget to check that it is actually long enough to stop the damper valve touching the underside of the damper tube top. In an ideal world it would be possible to give the required length, accurate to the nearest millimetre, but where old British bikes are concerned it is often unwise to be so precise. Each (possibly mixed-up) set of fork components should be measured for the best results. In fact, by experimenting with different damper rod and top bush (or spacer) lengths, it is possible to adjust the effective length and travel of Roadholders I quite easily. However, this should only ever be necessary if the forks are fitted to a non-original type of frame, when the ride height may be incorrect. The average home mechanic is advised to leave this kind of thing well alone.

Arranging a credible bump stop on full compression is even easier than providing one of full extension. All that is necessary is to block the existing holes in the lower section of the damper tube and re-drill them in a position just above the taper. The only question is, how to block the holes? Those with brazing or welding gear (and the skill to use it properly) will even now be reaching for their goggles and spark igniter. The rest of us will have to indulge in a bit of lateral thinking. A simple method is to tap the holes (say 8mm) and insert a suitable bolt or screw.Using Loctite, and with the bolt head cut off and the ends peened over, this works quite well. It can even look reasonable if the ends are dressed with a file, but as nobody is going to see the result it only matters that you preserve the taper and don't leave any metal protruding. The seal doesn't have to be totally oil tight either, although a good job will be and it is
as well to aim for this.

I use a simple piece of alloy rod cut to length, with the ends squashed in a vice after fitting and then filed smooth. Those of you with the earlier pattern tubes with four holes can obviously not use the bolt or rod method for the second pair of holes at right angles to the first. Instead, you can fit a collar over the lowest part of the damper tube to block off all four holes; this can be held in place by the taper above and the bottom of the slider below. Of course, it must be no wider than the taper at its widest point, so that the base of the stanchion can pass over it. Alternatively, the bottom of the four hole damper tubes could even be filled with Isopon or an epoxy resin, but I'm sure you can do better. Having blocked off the original holes, by whatever method, the two replacement holes (only two are necessary about 1/4 in.) can be drilled just above the taper, as in the original Matchless design. The position is not critical, as long as they are below the lowest point reached by the damper valve inside the tube: there is plenty of leeway, so just above the taper will do.

Having performed these simple modifications, your bike will have a set of forks the equal of most and better than many. On the neglected roads of the Eighties, the need for good damping at the extremes of suspension movement is becoming more pressing and as these alterations are totally concealed, they should not offend the purist or devalue your machine. Instead, they should give you that little bit more pleasure as you ride your classic.

Those of you ready, willing but unable to carry out these changes, will be glad to know that a kit of parts is available to do the job. The kit consists of two alloy bushes, four alloy dowels and fully illustrated instructions (in English, French, German and Dutch).

Editor's Note: This is an old article and Peter Crespin is no longer making the conversion kits. Peter's contact details are below and if there is enough demand they may become available again.

Peter Crespin
The Writers Bureau
P.O. Box 57
Buxton 
Derbyshire
SK17 7AE
UK

Tel: +44 (0)1298 27112
Fax: +44 (0)1298 71093
Cell: +44 (0)7973 854452
Web: www.thewritersbureau.com
Email: pc@thewritersbureau.com

Norton Commando Sprocket Change

posted 25 Dec 2011, 04:49 by NOC NSW   [ updated 25 Dec 2011, 04:50 ]

Degree of difficulty: *** (three stars), Time: 1 1/2 hours for an expert, if no unforeseen problems.

This description is based on a 1972/3 750. It is not very different for 70 to 74. Very early bikes may be different, I have never seen inside one. MKIIIs are very different. There are two Belville washers in front of the rotor on a 74 MKIIA.

Tools... Clutch compresser, sprocket puller, torque wrench, 1 1/2AF ring or tube spanner, various sockets including 15/16AF. No Whitworth needed.

Parts... crankcase to primary gasket needed, clutch circlip, inner primary seal and clutch tab washer optional.

*********

Find a calm frame of mind.

Remove the left foot peg (1/2AF socket and ext), do not hang it from the stoplight wires.

Undo the centre nut (3/4AF?) on the primary case and remove the outer, you will need to make arrangements for the approximately 180cc of oil in there. There is no drain plug.

Remove the stator, if the connection in the wires is hard to get back out of the hole in the inner, suspend it from somewhere higher up with a coathanger (a coathanger must be used once in every job; local custom). Do not allow it to hang from its wires or twist as the insulation gets very brittle from the heat. They can be re-insulated if broken, but it is fiddly.

Take the rotor off. (15/16AF) To do this you need to put the bike in 4th and replace the footpeg so you can use the brake to lock the wheel/chain/gearbox/clutch/primary chain/rotor. Behind the rotor there is a key, a spacer (note the way it goes on, with the recess out) and a couple of shims.

Ist special tool... you need a puller with two bolts (5/16 UNC?, about 100mm long) to screw into the front sprocket and one pointed centre one to bear against the crank. Get the sprocket started, but don't try to pull it right off, it needs to come off along with the clutch and chain.

Second tool... remove the clutch adjustment nut and screw, attach a clutch compresser, take up the spring pressure until the spring plate will rotate easily, remove the big circlip with a screwdriver and take off the spring. (Good opportunity to wash the plates, do it).

Undo the tab washer and the clutch nut (spark plug spanner fits). Slide the clutch, primary chain and front sprocket off as one, threading the stator through it if you have it hanging. Easier with three arms. Take off the shims and spacer behind the clutch, noting the orientation of the spacer (recess towards the circlip).

Take the woodruff key from the crankshaft, then remove the inner primary cover by undoing the three 7/16AF bolts. They have tab washers.

Remove the tab washer from the countershaft sprocket. (2BA screw) Lock the rear wheel and remove the nut (1 1/2AF), needs to be a tube spanner or a ring with cranked ring. Note that this is one of the few reverse threads on the bike.

Change the sprocket.

When putting it back together, it is sometimes hard to get the 2BA screw to line up with the holes in the sprocket. I have often had to loosen the nut slightly to get the screw in. I Loctite the screw.

This is a good time to change the felt seal in the inner primary, and the circlip on the mainshaft. I would not think of doing this job without changing them. I used to. The felt seal can be tricky, the secret is to compact it forcefully sideways at the same time as stuffing it in with a small screwdriver.

If there was more oil in the primary than you put in, it probably means the crankcase seal has gone. This is a good chance to change it. Get the seal out by drilling a couple of holes in the thin metal ring and hooking it out. put a little sealer around the outside of the new one.

Watch you don't lose the washers on the centre shaft that holds the primary covers, they are an adjustment.

When you have replaced the stator, you need to check the air gap between it and the rotor. 8 thou is OK all around. If it is tighter atone point, loosen the nuts, push the stator in the direction it needs to move and retighten. RE-check. Do not leave the bike with insufficient clearance here, it will wear a hole in your pocket very quickly.

The rotor needs to go to 70 ft lbs and the clutch nut something similar, although I only use 50 lbs here as 70ft lbs once sheered a circlip for me.

Things you can check on the way through if you have time and inclination are, the alignment of the inner primary, the alignment of the two primary sprockets. You can also flat the primary covers and renew the seal if sealing is an issue. The condition of the clutch hub and plates can be inspected also. It is worth looking to see whether there is oil coming down the pushrod from the gearbox. It smells different and can sometimes be seen radiating away from the tab washer. There are aftermarket fixes for this.

Put 180cc of oil in the primary.

Basic tools to get you started

posted 25 Dec 2011, 04:43 by NOC NSW   [ updated 25 Dec 2011, 04:44 ]

When your new to Norton's and you find it difficult enough to work out if a spanner is metric or imperial, suddenly finding AF and Whitworth in your world as well, might leave you a little confused. Heres a list to get you started.

The following list of essentials tools to carry for a 71 Commando Roadster comes from Chris Ghent. Don't forget that you should also have a C spanner for tightening up the exhaust pipes and a clutch puller, both available to members from the club's spares department.

Tools in italics should be carried on the bike, have fun working out there!

3/8 Drive sockets

2 small extensions (more versatile)

spark plug socket

Whitworth

1/4

5/16

AF

7/16

1/2

9/16

1/2 Drive sockets

AF

7/16

1/2

9/16

5/8

11/16

3/4

13/16

15/16

1 1/2

1 5/16

Double ring spanners

Whitworth

3/16 and 1/4

5/16 and 1/4

Ring and open spanners

AF

7/16

1/2 (x 2)

9/16

Whitworth

1/4

Double open spanners

Whitworth

1/4 and 5/16

Other tools

combination screwdriver set, large shifting spanner (rear-wheel), allen keys (including a modified short arm allen key to access the carbs).The next question is where to find AF and Whitworth tools. I'm reliably informed that Flemington markets on Saturday are a good bet for second hand tools. Try and get good quality tools like sidichrome.

Paul

P.S. Chris also supplied the following list of tools and advice

"I find I can fit all of this in the left side panel pocket and a small bag in front of the battery on the Commando. I commute and also do a couple of long trips a year. On the long trips I add a clutch puller and a head gasket. Haven't needed them yet.

shifter 10Ó spanners ...( 7/16 1/2 9/16 AF) (1/4 5/16 W), (7/16 AF is the same as 3/16W), plug spanner (a box spanner is light and the screwdriver can turn it), screwdrivers... small/ large slothead, posidrive. (Combination like the one in the original kit), allen keys... for carbs, ignition rotor, small socket set... including 1/4W and 7/16 1/2 9/16 AF, and extension to reach head nuts

Also carry a spare plug, some electrical wire, a coathanger inside the handlebars, electrical tape, 1/2AF nyloc nuts, other assorted nuts, bolts, washers, fuse, carb screw, chain link, circuit tester (sort with bulb, doubles as trouble light), silicone, if a Roadster carry a condom (for transferring petrol, did you think it was because Roadster riders are naturally more attractive?), Boyer troubleshooting guide from INOA tech tips and a Mars Bar.

Chris Ghent

Commando Wheel Offset

posted 25 Dec 2011, 04:40 by NOC NSW   [ updated 25 Dec 2011, 04:44 ]

Question sent into NOCNSW

I have just purchased a 1973 850 commando interstate. it came with re-spoked rims out of the bike, when fitted the offset lookes wrong, about 9mm to the left, sitting on bike. Can you tell me the offset for the wheels and who is the best for spareparts and tank re-spray?

Answer from Geoff

The engine, engine/gearbox plates, gearbox, swing arm and rear wheel hub are offset about 1/8” to 3/16" to the left. The rear wheel rim should be laced with an offset of the same to the right to bring it back onto the centerline of the bike.
The front and rear rims should end up on the centerline of the frame. The spokes beside the front disc should be nearly vertical.

You can see some actual offset measurements here:
http://www.kolumbus.fi/norton/norton/frontalign.jpg
http://www.kolumbus.fi/norton/norton/rearalign.jpg

From the UK Norton Website:

Commando wheel offset - the definitive answer
I have the definitive answer as to what is offset, how much, and which way! 
I set up a 1973 850 on the frame table and verified it was straight. I then put together a dummy engine and installed it with new isolastics, new washers, Hemmings adjusters, and a Norvil head steady. I put both adjusters on the left side, checked the swinging arm in my fixture and then installed it in the frame. I took all the play out of the adjusters and started measuring:- 
The frame is symmetrical 
The engine/gearbox cradle is offset 1/8" to the left. 
The swinging arm is offset 1/8" to the right so the axle pads end up centred in the frame 
I then installed the rear wheel:- 
The spoke flanges are offset 1/8" to the left as mounted in the arm, so the rim is laced off 1/8" to the right to put the tyre in the centre 
The centre of the rim is 3.3/8" from a straight edge laid across the brake drum (not the backing plate 
http://www.nortonownersclub.org/technical/commando/offset_detail.html


As for spare parts, Eades (9798 7822) are the only shop left in Sydney. They are reducing their opening hours, however they do mail order.
You may find Ryans (6558 8195) up at Gloucester a bit cheaper. They are mail order only but provide good service.
There is also British Spares in New Zealand (+64 4 939 8819) who are very competitive price-wise and also give good service. http://www.britishspares.com/

Painting:
The Keed brothers in Arncliffe are renowned for their good jobs, but they take a long time and are a bit expensive.
Ph no. 9567 5422 address: 54 Lower Wilson Rd Arncliffe.

Regards,
Geoff

Note: since this article was written Eades is under new management and is now Eade Classic Allparts and Ryans has ceased trading - NOCNSW Web Editor

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