I"ve had a miss on my Farmall 340 when it was under full load. It would miss for a short interval (stumble). Then,if I backed off the throttle it would recover and then run fine for awhile again. Been trying to find that miss for quite awhile and its been driving me crazy (short trip there!). Always seemed like gas to me so, I set the carb float to specs and cleaned it all out. No change. Tried all the other likely stuff like clogged gas lines, spark plugs,etc.
Turned out it was the carb float, but not the float setting. The float was rubbing the bottom of the carb bowl. This caused it to not lower far enough to fully open the float needle valve. Ran just fine until it needed more gas than then the partially closed needle would let into the bowl then it would miss because it was starving for fuel. Took me a few trys to get that float to not hit the bowl. It was pretty hard to tell if its hitting or not. I had to hook up a rubber hose to the gas line fitting on the carb and while the carb was on the bench i could blow through the hose and be able to tell if the valve was fully opening or not. Seeing how finicky the float adjustment had to be, made me think that the float rubbing issue may also be the hidden cause of many of unexplained overflowing carb problems. It just plain old hard to tell if that float is rubbing. Anyhow, I mention this in case it can be of help to anyone else. Pete
Turned out it was the carb float, but not the float setting. The float was rubbing the bottom of the carb bowl. This caused it to not lower far enough to fully open the float needle valve. Ran just fine until it needed more gas than then the partially closed needle would let into the bowl then it would miss because it was starving for fuel. Took me a few trys to get that float to not hit the bowl. It was pretty hard to tell if its hitting or not. I had to hook up a rubber hose to the gas line fitting on the carb and while the carb was on the bench i could blow through the hose and be able to tell if the valve was fully opening or not. Seeing how finicky the float adjustment had to be, made me think that the float rubbing issue may also be the hidden cause of many of unexplained overflowing carb problems. It just plain old hard to tell if that float is rubbing. Anyhow, I mention this in case it can be of help to anyone else. Pete
