McCormick Deering 10-20 Does Not Start When Hot

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RegularJo

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I’m having issues starting my ’28 McCormick Deering 10-20 when hot. The tractor can be difficult to start when cold also, but it’s almost impossible to restart when hot. I initially suspected coil or condenser trouble, but I’ve checked spark on all plugs when hot and receive a nice, fat, blue spark at each plug. I’ve actually had two magnetos on the tractor and have experienced the same problem with each one. Originally I had an F4 mag but replaced it with a rebuilt E4A for originality purposes. I set the timing with number one piston just a hair past TDC to prevent kickback as I do on all my other hand cranked tractors.

I’m now wondering about the valve clearances since I’m having the most difficulty when hot. The valve clearances are set at 0.011 hot per the owner’s manual. To me, this value seems a lot lower than the clearances I’ve seen in other IH engines. What valve clearances are some of you running in your 10-20’s?

Any other suggestions as to what else may be causing the hard starting issue are welcome. Thanks in advance for any help!
 
I found in the archives that its .010"-.011" , but that sure sounds a little tight compared to the bigger Farmalls at .017". Hal
 
A fat blue spark is pretty much an elimination of the spark as the issue. I suspect it is getting too much air, and too little fuel. If it has a leaky intyake manifold, or a crack (internal) in the manifold it will be difficult to start. I would begin with that issue.
To see if it is fuel related, use a propane torch, and put some propane/air into the intake manifold, (possible have a helper) then crank it. If it fires up, it either needs more choke when hot, or it mught be an indication of an intake vacuum leak. Jim
 

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