Farmall m

rkbenish · Mar 4, 2016

My m has all new parts from the gas tank to the carburetor and it still can't get to high rpm's. It only runs when fully choked and when idled up it dies.

Janicholson · Mar 4, 2016

Flow from the fuel line to the float bowl (I assume you have the screen at the carb inlet clean) is through a right angle passage in the upper carb casting. This elbow can get plugged. Also the seat brass fitting can have trash above the needle limiting fuel. A third issue is a main jet that is plugged. another issue might be the venturi put in upside down or missing. These should be checked in about that order to get to the heart of problem. Jim

glennster · Mar 5, 2016

Did you by chance install an after market in line fuel filter? If so try taking it off.

casecollectorsc · Mar 5, 2016

Assuming you did try opening the load needle another 1/4 turn to give it more fuel.

showcrop · Mar 5, 2016

Before replacing all the parts you should have shut the gas off at the tank, set up a means of catching gas from the bottom of the carb, removed the float bowl drain, then turned the gas back on and insure that a steady stream would run for a half minute. Is there a filter inside of the tank?

jal-SD · Mar 5, 2016

Is the governor shaft in the notch on the carb? Not getting that shaft in the proper place on an H carb can cause similar problems-could improper placement cause the same problem on an M? (My $0.02 worth. jal-SD)

Steve@Advance · Mar 5, 2016

That it will only run fully choked is an indication of too lean. Could be a restriction in the main jet circuit, low float level setting, restricted fuel flow to the bowl, missing or improper part assembly.

There is a plug in the bottom of the carb. With the fuel valve on, remove the plug. There should be a full stream flow until the bowl begins to empty, then slow to a trickle. If it stops or slows to a drip, there is a restriction between the tank and the bowl, or the float level is too low. Catch the fuel in a clean glass, look for contamination or water settling to the bottom.

All fuel passes through the main jet. The flow is then divided between the idle circuit and the power circuit. Since it trys to idle, that circuit must be getting some fuel. Look at the power circuit, the brass tube that extends into the center of the venturi ring. Be sure the tube is in place and is open, be sure the venturi is in place and is not upside down. It may go in either way, but will only fit properly one way.

504 · Mar 5, 2016

Pull the plug from the bottom of the float bowl and let the gas run,give it 1 good minute, and make sure it is still running a full stream. Anything less, just start looking for the restriction,if it flows fine it has to be internal to the carburetor.

Farmall m

rkbenish

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Janicholson

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glennster

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casecollectorsc

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showcrop

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jal-SD

Well-known Member

Steve@Advance

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504

Well-known Member

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