TO-20 Carburetor Question

pburchett

Member
The original carb on the TO-20 was in rough shape after going through a fire. I cleaned it out and resoldered the float. Never could get the needle valve to seat so I purchased a new aftermarket carb and cleaned it well.

The tractor runs well except for the fact that it stumbles when you open the throttle up. Does not matter if the engine is warm or cold. I have adjusted the main jet with no success. I do have the float set a little lower than called for as I was hoping to avoid the dreaded fuel overflow in case the needle valve didnt shut the gas flow off properly. Any suggestions?
 
My TO-20 has been in the family since 1956, and I recently overhauled the engine and carburetor. When you opened the throttle quickly it stumbled before I rebuilt the carburetor, and stumbles now. These carburetors don't have an accelerator pump, so you have to advance the throttle slowly.
 
(quoted from post at 04:53:41 08/21/21)
How much is a "little" ?

The manual calls for 0.28 inches from the gasket to the float and I set it at 0.33 inches.

If the float can cause the stumble I will readjust it and reclean the carb.
 

The old carb did not stumble but the new one does?

Might have to put the new float and needle valve/seat in the old carb.
 
Set the float by the specs, that will make a difference.

Compare the size of the venturi. The aftermarket carb could be a fit all designed for a larger
displacement engine.

Be sure the distributor is good, the shaft can't have any side play or the points won't stay set.
Be sure the centrifugal advance is free and working. Try playing with the timing, you will know
when you find the sweet spot.

Have you cleaned the wire mesh inside the air cleaner? Often overlooked, if really packed it will
have to come apart. Not easy but necessary.

Part of the carb adjustment procedure is setting the main jet. With the engine fully warmed up,
thermostat in place, tuned, valves adjusted, let the engine idle down to around 400 RPM. Set the
idle adjust for best idle. Then start adjusting the main. Start lean, suddenly open the throttle,
if it hesitates, open the jet adjustment 1/4 turn at a time, keep repeating until it will take
sudden throttle without hesitation. A single puff of black smoke is the goal.
 
Steve@Advance is the winner.

It was the venturi. The one in the new carb had a larger inner diameter that the old one. Swapped them out reset the float and it runs fine now.

Every thing else was good such as the distributor, and air filter as I have been rebuilding the tractor from back to front.
 

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