Heating problem

37chief · Jul 2, 2016

I was having a heating problem on one of my AC Model M's. I was checking the timing, and found the piston was just over TDC when the mag fires. Could late timing cause heating problems? Stan

Bob · Jul 3, 2016

Yes, late timing can cause overheating.

Mag timing should be at TDC, or slightly after to avoid kickback.

Once the engine "catches" and the impulse drops out, the mag reverts all at once to "running timing" with no further speed advance.

So, if cranking impulse timing is correct and the lag angle of the impulse is correct, running timing should be correct, as well.

John T · Jul 3, 2016

I agree with Bob that too fast timing can cause temp to rise, but I'm not sure if you checked start/impulse timing (ONLY when starting) or the run time advance once shes up n running usually over 250 RPM or so when the impulse spring wind n trip mechanism stops working. If the start/impulse is before TDC she will kick back as Bob was talking about, but its the long term run time advance timing being too fast that can cause temp to rise and a mag and/or lag angle would have to be pretty far off to cause that. A timing light and a timing reference mark at TDC and then say 10 to 30 BTDC can show where shes running at and the start/impulse needs to SNAP right at TDC. Too fast timing makes the engine run harder and LOUDER and sound likes shes laboring under a load even if theres no load whatsoever. Sorry I have no info on your Mag so the above is just general info.

John T

El Toro · Jul 3, 2016

Running an engine lean may cause overheating. Hal

David G · Jul 3, 2016

Late timing would be too slow.

John T · Jul 3, 2016

YES and the reason why is because air (lean) cant transfer heat out of the cylinders as well and a liquid or vapor (richer) can. One of the few things I remember from Thermodynamics class yearsssssssssss ago lol

John T

dr sportster · Jul 3, 2016

Late timing = heat build up.

Steve@Advance · Jul 3, 2016

What kind of heating are you having?

Boiling over? Heat by the gauge? Smell?

Slow ignition timing can cause high exhaust temps, as in getting the manifold and pipe extra hot, which could cause unusual smells, heat radiating from the engine, vapor lock, even danger of fire if grass were near the exhaust or the gas tank were to boil over!

Not sure how the mag is driven on that, but if it is driven off the cam, and the cam timing were also retarded, as in sheared drive key, jumped chain (if equipped), that can cause the engine to overheat, especially if being pushed hard.

But, either case, the idle, starting, and power would be effected.

Heating problem

37chief

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Bob

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John T

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El Toro

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David G

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John T

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dr sportster

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Steve@Advance

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