T120 spark pattern - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 2 (permalink) Old 05-17-2017, 10:38 PM Thread Starter
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T120 spark pattern

I have a new 73 t120 with new condensers, dual 12v coils, and plugs. Are the spark plugs supposed to fire together at the same time? I have both plug out checking spark and one will fire then the next will fire but not at the same time. Sorry noob here to these triumphs I just figured since the Pistons are in sync the plugs should be too?
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post #2 of 2 (permalink) Old 05-18-2017, 12:26 AM
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The engine in your Triumph is a '4 cycle engine" The spark occurs every other revolution of the crankshaft.
The pistons rise and fall together, but they are on different cycles. The four cycles being suck, squeeze, bang, blow.

So as you state you have condensers on your bike and I presume are still using the points ignition, the spark will not occur at the same time.

Englishman in Japan
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