No spark on two plugs 85 Aspy

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No spark on two plugs 85 Aspy

Post by tricky » Thu Aug 02, 2018 1:09 pm

I am attempting to chase down a problem hoping that someone can help jog the brainwaves a little.... or maybe a lot :)

The left coil that services plugs 3 & 4 will not produce a spark. The right coil servicing 1 & 2 plugs is fine.
The coil was tested by aircraft electricians who no doubt have better instruments than I, they tested several coils and found all of them that I had to be within spec.
I am troubleshooting with the 85 electrical manual.

Steps 1,2 & 3 page 142 pass muster , there is voltage on the black & white wire on both coils.

step 4 is where it seems to be not quite right.

Connectors 69/68 (black/white wire) coming from engine stop switch is providing voltage

Connector 67 (Yellow/blue) Right coil provides a bright pulsing light when the engine is cranked. (OK) spark at plugs 1 & 2

connector 70 (Blue/yellow) left coil showing a very weak pulsing light when engine is cranked, no spark at plugs 3 & 4 (I have tried swapping coils from my supply)
Just to be sure, I will swap the coils on the bike knowing the right one to be providing spark and see if the results change.

New wires and plugs.
Swapped IGN CTRL unit with another (same result)

Hoping someone can give some insight as to where I can test.

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Re: No spark on two plugs 85 Aspy

Post by virgilmobile » Thu Aug 02, 2018 2:06 pm

The pulse coils(pulse generators)...
There's 2 of them.. Measure there resistance from the ignition module and again where they plug in from the engine to the harness.
Suspect one is out of specs or corrosion at either plug.
There is a very small voltage on these and any corrosion will weaken the pulse.
Also you didn't mention what the voltage was on the black/white wire.While cranking it should be no more than 1/2 volt lower than the battery.

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