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Ignition Timing for Commando With Boyer

posted 25 Dec 2011 04:36 by NOC NSW   [ updated 25 Dec 2011 04:46 ]

Ignition Timing for Norton Commandos is 31 degrees BTDC @ 5,000 engine revolutions per minute for Boyer electronic ignition systems, and 28 degrees BTDC (5/16”) fully advanced @ 3,000 engine revolutions for ordinary points-based ignition, both set with a stroboscope.  NB.  Use an external power source for the stroboscope or you get feedback and this distorts the reading.

INOA (International Norton Owners Association – www.inoanorton.com) have a good article on their website, with advanced curves for points-based centrifugal ignition systems, and Rita and Boyer electronic ignition systems.

One of the main problems I have encountered with the Boyer system is that full advance (31 degrees) does not occur until 5,000 engine revolutions and at that engine speed, everything is bouncing around and stroboscopic readings are pretty hit and miss as to their correctness.  To get a reading at lower revolutions and generally make setting the ignition timing easier, I have taken readings from the Boyer Curve at lower engine revolutions and they appear below.  Be aware that these assume that your Boyer advance curve is programmed correctly.  As I make it:

Engine Revolutions    Boyer Advance

1,000                                      6.3 degrees (6)*

1,500                                    11.4 degrees (11 or 12)

1,800                                    14.7 degrees (15)

2,000                                    16.3 degrees (16)

2,500                                     19.6 degrees (20)

3,000                                    22.8 degrees (23)

3,500                                    26.1 degrees (26)

4,000                                    27.7 degrees (28)

4,200                                    29.4 degrees (29 or 30)

4,500                                    30.0 degrees (30)

5,000                                    31.0 degrees (31)

 *Bracketed figures are practical readings when using a stroboscope.

Note the big jump in advance between 2,000 and 3,500 engine revolutions – 10 degrees, while for the next 1,500 engine revolutions (to 4,500) it jumps only 4 degrees!  So try strobing it at 23 degrees @ 3,000 engine revolutions or 26 degrees @ 3,500 engine revolutions.  The latter should give a slightly more accurate reading and it certainly makes life easier when setting your Boyer electronic ignition timing!

Perce Butterworth