Ignition Timing for Commando With Boyer

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