fuelman8

I've got a walbro 771 and when I have it open full throttle fuel is blowing back out of the carb.

Do I have the end point on my radio set to high or is there another problem?

lildude2599

That carb is a 12.7 mm venturi. You may have it too rich try to lean it and see if it doses it again.


http://wem.walbro.com/walbro/product...m=WT%2D771%2D1

juicr

Some spit back is normal.

fuelman8

Thanks for the info guys

martno1fan

stick the spit tube back on and problem solved

fuelman8

Mart

I haven't taken anything off the carb and i'm still not sure where to even look for the spit tube.

martno1fan

the black plastic thing sometimes called a velocity stack

OLD_SLOW and in the WAY

tuning your intake length will stop the blow back, i wont go into the math here but its approximately 3 7/8" from the piston face to the end of the spit tube. basically you are overcoming the mass of the blow back with the inertia of the air entering the intake tract. if you run a can muffler then a Hemholz resonator will give you a 15% boost which is about what a tuned pipe gives an engine. ive done extensive testing with these devices and they come on like a shot of NOS. plus they will prevent you from hydro'ing the engine in a roll over.

fuelman8

Thanks Mart & Old and Slow good info

I have a velocity stack I ordered seperate from the motor, but I didn't put it on because the fuel tank is in the way. I think i'll check into going with a gas bag I can locate elsewhere.