M Farmall sputter

I have been tinkering with an M Farmall -- It starts good and runs good for ten minutes then it spits and pukes till it dies -- checked every
ting and came to the conclusion that the one or two valves hang up -- it spits out the intake to the point the oil in the air cleaner blows
out the top -- not good! this was a rebuilt head two or three yeas ago -- I would imagine the the valves are all carboned up -- wondering
what You guys think ---- is there something a Guy can do to get her back to normal? Roy

I'd try 1 quart of ATF to 3 gal of gas and see if that cleans things up

Kinda unusual for valves to stick on a running engine, and then unstick on their own. Might check the valve lash if it hasn't been checked since it went back together. That would give you a chance to look the valve train over. Be sure all the valves are opening equally and no broken springs or bent pushrods. But I'm guessing all will be well, as valve problems generally are not intermittent.

Intake backfire is typically caused by lean mixture, weak spark, cross fire, retarded ignition timing, a flat exhaust cam lobe will cause rhythmic backfire under load.

Cross fire can be caused from condensation under the distributor cap. If there is water trapped in the distributor, often it will boil up when the engine gets warm and condense under the cap. Then it dries out when it cools, repeats if still water in the distributor.

Weak spark can be failing points, failing condenser (very common bad new in the box), failing or wrong coil (wrong coil or coil/resistor combination).

Worn distributor bushings can cause the point setting to change, do strange things. Also can a stuck or sluggish centrifugal advance will retard the timing.

Have you checked the fuel flow through the carb bowl when it acts up? Should get a steady flow through the drain plug.

I agree with-OLD. Try a little upper lub . That is a good mix.. Valve is free in guide when cold, but guide warms up and tightens up on valve... Try some lub????

Fuel issue. IF not fuel, condensor. Its not going to shut down IF a valve is sticking.

Had an M do the same thing many many years ago. I ran the tank low and loaded it up with marvel mystery oil. Put some in the crankcase as well. Took a little while, smoked and finally came around. It had set unused outside for several months loaned to a supposed friend. No cap on the exhaust when I went to get it as he did not seem interested in bringing it back. Never happened again.

What are you doing with the tractor during the 10 minutes? Have you used this tractor to do any type of work? I agree with John that is likely a fuel problem. I think it was Grandpa Love that recently had a tractor that he just picked up that was not running good at all. In the end he determined it had valves stuck open in 3 of the 4 cylinders but it kept running.

I was ready for all kinds of reasons why it wont run and I checked it all -- it has electronic ign. and the spark is hot all the way till it dies --the gas flow is good -- pulled the plug out of the bottom of the carb. and it filed a pint in less than 30 seconds -- and I know how to adjust a carb. -- when it blows the oil out of the air cleaner when it backfires i know it is a sticking valve -- so the issue is what to do about it ! thanks Guys Your the best! Roy

Electronic ignition is going bad simple as that

Hi Old --so do You think the electronic ign.is firing when it is not supposed to causing the backfiring ?

Yes it could but also the fact that after a few minutes it dies say the electronic ignition is going bad and as it heats up stops working as it should and yes can fire at the wrong time

I agree that the electronic ignition may be failing and causing your issue. I would personally try sticking points back in it temporarily to prove that is the problem. Valves sticking would have some additional mechanical noises associated with it are you hearing anything like that?

If you had mentioned the EI to start with, the answer would have been much simpler.