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312Icarus
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Joined: 07/15/2016
Posts: 409

I put a cheap inductive tach on my /2 and while it seems to be right at idle, it is way off at speed. My stupid question is this...do both plugs fire at the same time (with a “sacrificial” spark) at that top of the exhaust stroke as well as the top of the compression stroke. I know that the coil is actually two coils in one housing, but since the mag spins round once each rev (and the points open) I assume that both coils fire. This matters because the configuration of the tach is such that you have to tell it it if sparks once per rev, twice per rev, or once every other rev. The pick up for the tach is simply induced from one plug wire. I assumed that it was once every other rev but on sober second though, I think it is once per rev.

Thanks, for all advice,

Icarus

schrader7032
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VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6790
The plugs fire in a wasted

The plugs fire in a wasted spark situation...both plugs fire at the same time. They fire once per revolution of the crank. Thing about when you set the valve clearances. For example, you set the left side valves at TDC. To set the right side you rotation the crank 360 degrees to get to TDC on the right side. Note that just before each of these TDC points, the plug would have fired...at idle it's 6 (or 9) degrees BTDC.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

312Icarus
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Joined: 07/15/2016
Posts: 409
Thanks Kurt..that is what i

Thanks Kurt..that is what i figured.

Tony

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