RandyB(MI)
Well-known Member
DLTX 67 carb on JD late "B". Complete rebuild inc new float, steel needle / seat. Float level set on bench first with fluid and sealed perfectly. Mounted loose on test tractor, turn fuel on fills up and runs full stream out front of carb. (this is why I mount loose first) After hour of re-checking everything I took complete bowl off a perfect 71 that i knew was right and put it on. Same thing! Switched back and with fuel level check tube on, turned on fuel, way over top edge of bowl. Over filling but eliminated whole bottom of carb. What , in the body of the carb, would cause the fuel to overflow and run out ends of carb? Well I found out what caused it . Have never seen it before and have never seen it on any how-to vids or even on here. It was plugged , in and just above the two baffles in the bowl vent port (top or roof of bowl) The way I found it was I threaded the load needle out all the way (which will vent the bowl) and re-checked the fluid level tube and opened up the fuel and it set right there at 5/8" right where it belonged. What was happening was the bowl wasn't actually filling up over full. It was filling up to correct level but it was pressurizing the air above it and forcing fuel through the tiny idle needle port and the tiny load needle port (about 1" off bowl floor) and up through the load nozzle into throat and up through idle passages and out through throttle plate idle ports into throat leading one to believe the float bowl was full and overflowing. When using the level setting tube, it showed way over full also because the pressure,not volume, was what was pushing the fuel up the tube. You have approx. 12 psi air pressure and the pull of gravity compressing the air / fuel in the bowl and once above the ports, the air can't escape so fuel is forced out since you don't have the 12psi coming in from the vent to neutralize the incoming pressure. So all those posters on here complaining about their "new" needle/seat float not shutting fuel off and filling crankcase, may NOT be the "junk " needle/seats in every case. Who would think just a little vent port plugged would overflow your carb and fill your crankcase ? Drove me nuts for a while.