Farmall A runninrg rough

Doggonetractors · Mar 17, 2009

I have a questions for the pros. I have a Farmall that just had a complete engine rebuild and the head was completely rebuilt. It runs rough at Idle but when I put choke half way on it runs perfect. Why is it doing this? I have a brand new carb and adjusting makes no difference, Rebuild Mag and the timing is set perfect, Valve lash is set perfect, Brand new airfilter assembly, All new gaskets. I don't know what else to do. Thanks.

Anonymous-0 · Mar 17, 2009

Might be a good idea to take the carb apart and check it out. The fact that you're sure that all timings are right, and, when you richen it up with the choke it's OK, says that either the new carb is defective or some dirt got into the jet somewhere along the line. There are other possibilities s/a cam timing, but you sound sure about that. I had the same issue with an Allis B...took the carb apart, cleaned, still had same problem. Swapped the carb out, runs like a champ.

El Toro · Mar 17, 2009

Its starving for fuel. Make sure there's a good flow out of the tank to the carburetor. If it has an inline fuel filter take that out. Check the float level too could be set too low. Hal

ScottyHOMeY · Mar 17, 2009

Could also be too much air, coming from a leak either between the manifold and head, or the carb and manifold.

TractormanNC · Mar 17, 2009

Does it run good at full throttle? If so and you have exhausted all the others advice, here's the problem.

An A or SA with a mag and flattop pistons runs a 40 degree impulse coupling which gives full spark advance as soon as it is running. If it was rebuilt with domed pistons this is too much spark advance. Replace your mag impulse coupling with a 20 or 22 deg if you can find it. The best thing to do is get a battery distributor with a 20 or 22 deg shaft and put it on.

BTDT.

tractorsam · Mar 17, 2009

I'd shoot for a carb problem or intake manifold leak. I was working on a cub last weekend that ran fine with partial choke but ran poorly or died with no choke. Tightend down the manifold and away we went. Sam

Doggonetractors · Mar 17, 2009

Thanks for all the input guys.

LMack · Mar 17, 2009

I did this for my 200 that was rebuilt. On first crank, I had the distributor set loose. Once running I adjusted the time until it ran correct (set by ear). I had new pistons and I am not sure if they were domed, but my time set was at least 15 degrees off and I had checked and rechecked to be sure I had done it according to the manual. If that does not work, try swapping out the carburetor from a running tractor. If that fixes the problem, it was the carburetor all along.

chad from michigan · Mar 17, 2009

Just bought a Farmall A real cheap guy got tired or trying to get it to run right. He claimed it has always had to be half choked to run and was tired of it.
I got it home and played around. Found out that the sediment bulb was jammed and after screwing it in and out found out it opened 1-1/2 more turns and it fixed the problem. Got a great deal and even better when I opened the bottom drain on the carb it the gas trickled out pull the plug and make sure its a steady flow of gas.
if not check your fuel flow. If it has an in-line filter on it like many people have added take it off those are bad news for those tractors.

Farmall A runninrg rough

Doggonetractors

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Anonymous-0

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El Toro

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ScottyHOMeY

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TractormanNC

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tractorsam

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Doggonetractors

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LMack

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chad from michigan

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