1936 A misses on timing light

Ken11487 · Apr 17, 2012

Was setting the timing on my 36A with a timing light the other day and noticed a miss in the timing light as well as the engine. Shouldn't the light (and engine) fire EVERY time?
You can count the firing. Maybe 20 flashes then a miss or two. Very irregular.
Can the coil get weak? How do you test for this?
The points look clean. How can you tell if the condenser is ok?

You can hear an irregular miss going down the road too. The tractor seems to work well driving a thresher, but I think it could be better.

Earl-IL · Apr 17, 2012

Unless you run a magneto on a magneto machine with a adjustable spark bar, about the only way you can catch a miss is with a timing light.I do magneto repair & have a Allen variable speed drive. Just coming off the impulse, (speed) is a magneto's weakest point. XH & C model Wico fire on exhaust & compression stroke. Running your tractor full throttle does it still miss?

John T · Apr 18, 2012

The kickback test using an old fashion analog ohm meter will show if a condensor is definitely bad (shorts or opens) BUT IT WONT TELL YOU IF ITS GOOD (i.e. under actual higher voltages and at temperature). To better test a condensor you need an actual capacitor tester. For no more then the cost I would just try a new one.

If its a Wico C mag they have been known to have a short where the spring on the points (especially a cheap set of points) goes around the post then terminates.

There can be cap and rotor problems or carbon traces or cracks, make sure all that is clean and dry free of oil, moisture, traces or hairline cracks.

Yes coils can go bad but Id first suspect a cap or rotor problem (HV is shorting/arcing somewhere)

Sure the plug wires arent the problem including the small one on the cap on a Wico C?? Have it running in the dark and look and listen closely for sparks or pops..

John T

Ken11487 · Apr 18, 2012

I should have said its a Wico X mag.
It still misses irregularly at full throttle. You can count 20 or so hits then a miss.
I have new solid copper wires. The cap looks ok there are no tracks that I can see but I've never seen what a bad one looks like.
I'll try a new condenser and look into getting a new rotor and cap or may borrow a known good one first.
I like the running in the dark test but i think my prob is inside.

1936 A misses on timing light

Ken11487

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Earl-IL

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John T

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Ken11487

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