- Joined
- Nov 11, 2014
- Messages
- 65
hey folks
i recently bought a copy of jim schmidt's Norton Race Manual to see what it would say about my 70 commando, and discovered this intriguing bit about shortening the spark curve on boyer ignitions:
now this is useful to me not because i'm going to try it on the norton, but because i have a triumph with a problem it might solve. that machine has good breathing, a 9.5 to 1 compression, and a dual-spark plug cylinder head. i've tested it extensively with a stopwatch, and the best fully advanced timing is at 30 BTDC, down 8 degrees from triumph's standard setting of 38 BTDC. since i run a boyer, retarding the high rpm advance means i also retard the low rpm advance by the same amount, and so my triumph is a bit soft on the bottom end.
schmidt suggests that i can run a resistor between the two wires leading from the stator to the ignition module, which he says will retard the total advance available from the unit. then when you re-time the full advance, the result is that the low speed setting is advanced by the amount that you have shortened the total curve.
i haven't tried this yet. has anybody done it here? if you did, what were the results?
i recently bought a copy of jim schmidt's Norton Race Manual to see what it would say about my 70 commando, and discovered this intriguing bit about shortening the spark curve on boyer ignitions:
now this is useful to me not because i'm going to try it on the norton, but because i have a triumph with a problem it might solve. that machine has good breathing, a 9.5 to 1 compression, and a dual-spark plug cylinder head. i've tested it extensively with a stopwatch, and the best fully advanced timing is at 30 BTDC, down 8 degrees from triumph's standard setting of 38 BTDC. since i run a boyer, retarding the high rpm advance means i also retard the low rpm advance by the same amount, and so my triumph is a bit soft on the bottom end.
schmidt suggests that i can run a resistor between the two wires leading from the stator to the ignition module, which he says will retard the total advance available from the unit. then when you re-time the full advance, the result is that the low speed setting is advanced by the amount that you have shortened the total curve.
i haven't tried this yet. has anybody done it here? if you did, what were the results?