H missing badly when warm

Yellott Canby · Jun 18, 2009

My 1941 Magneto equiped H misses very badly when it gets warmed up. By warm I mean working in the field for an hour or so. It is definatly an ignition miss. On the mag I have changed the points, condenser, coil,dist.cap and rotor.The spark plug wires are nearly new and the plugs are brand new. The only thing I can think that is left is the square cap on top of the mag. Is there something else in the mag that can cause missing in warm conditions. Misses bad enough to have to drop many gears to do the same job. Generally raking or pulling a side-dress sprayer.
Thanks, YC

Bob M · Jun 18, 2009

YC - Sounds like that your mag coil is going away (the spark weakens) as it warms up. It's not unusual for a 60 - 70 year old magneto(!)

The coil sits under the square cap atop the mag body and is easily swapped out right on the tractor. Figure $50 or so for a new coil.

El Toro · Jun 18, 2009

Pull one of plug wires when it quits ASAP and see what the fire looks like from the plug as someone tries to start the engine. Check that valve lash too. Hal

Janicholson · Jun 18, 2009

Though spark issues are likely, a loose intake manifold (or cracked) can act like that! JimN

Yellott Canby · Jun 18, 2009

Hello. Thats what I figured so it was the first thing I changed. I suspect the new one has less than 10 hrs on it.
Thanks

H missing badly when warm

Yellott Canby

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Bob M

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El Toro

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Janicholson

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Yellott Canby

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