So my buddy picked up a 4R73C 4 hp at a yard sale for $20. She looked in decent shape, why not right? After checking it out it was apparent someone had done some head work, as a new gasket and sloppy gasket maker was visible. We tried starting her only to find she'd sputter briefly and die. So, we did the following:
* complete carb teardown, soak and rebuild with OEM kit
* float drop set to 1.375"
* new spark plugs
* new carb/intake gasket
After doing this work we pulled, pulled and pulled some more. She'd fire occasionally and quickly die. It sounded like fuel starvation. We ruled out spark by checking spark quality, removing the flywheel, inspecting points and checking wires. Spark is good.
We found the best luck when we set the high speed needle to 1/2 turn and low speed 1/4. This led me to believe fuel was leaking by the seat, so we tore the carb down again, inspected everything, double, triple checked, then pulled a vacuum on the bowl with it inverted. Everything checked out.
Next I pulled the fuel pump (had already checked screen), inspected the mating surface of the gasket to the crankcase and to the pump housing. All looked well.
Carb back on, problem still there. Pull, pull, pull, she'd sputter and die right out.
So we pulled the carb and then the reeds. Reeds are in shape and functioning properly. Next I pulled the head. No blowby, no water intrusion, no scoring on the cylinder walls and minimal piston play.
We are at a loss with this one. Usually after a carb rebuild on these small engines I set the low speed needle to 3/4 out and the high speed to 1-1/4, then tune from there. We tried that. We tried a whole slew of arrangements.
What are we missing?! It has ot be something simple. I figured it was in the carb - we overlooked, or missed something, but I am telling you we double, triple then double checked again...........
Thoughts, suggestions GREATLY appreciated. Thanks guys!
* complete carb teardown, soak and rebuild with OEM kit
* float drop set to 1.375"
* new spark plugs
* new carb/intake gasket
After doing this work we pulled, pulled and pulled some more. She'd fire occasionally and quickly die. It sounded like fuel starvation. We ruled out spark by checking spark quality, removing the flywheel, inspecting points and checking wires. Spark is good.
We found the best luck when we set the high speed needle to 1/2 turn and low speed 1/4. This led me to believe fuel was leaking by the seat, so we tore the carb down again, inspected everything, double, triple checked, then pulled a vacuum on the bowl with it inverted. Everything checked out.
Next I pulled the fuel pump (had already checked screen), inspected the mating surface of the gasket to the crankcase and to the pump housing. All looked well.
Carb back on, problem still there. Pull, pull, pull, she'd sputter and die right out.
So we pulled the carb and then the reeds. Reeds are in shape and functioning properly. Next I pulled the head. No blowby, no water intrusion, no scoring on the cylinder walls and minimal piston play.
We are at a loss with this one. Usually after a carb rebuild on these small engines I set the low speed needle to 3/4 out and the high speed to 1-1/4, then tune from there. We tried that. We tried a whole slew of arrangements.
What are we missing?! It has ot be something simple. I figured it was in the carb - we overlooked, or missed something, but I am telling you we double, triple then double checked again...........
Thoughts, suggestions GREATLY appreciated. Thanks guys!