Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Do you have good fuel flow to the carburetor? Is this gravity flow fuel supply? Did old engine have a fuel pump? The stalling is indication that there is not enough fuel to the cylinder.
Remove fuel hose at the carburetor and check for 1/4 cup of flow in 15 seconds.
Is the governor opening up when it hits load?
The governor has to move the throttle linkage at the carburetor , and when you hit load, the governor should move throttle to wide open position , so it will develop horsepower.
-Governor may not be working, or again, fule supply is restricted to the cylinder. There is no other reason engine would just die, unless you have a fuel solenoid in the carburetor.??
I doubt that the carburetor has any adjustment other than idle screw.
The main jet determines how much fuel enters the engine, and with choke making no difference, I question the fuel to the carburetor bowl.
Float and needle valve only control fuel into the bowl, the center post in the carburetor is the main jet, and the bowl bolt that screws into it. Be sure the needle valve passage is not restricted from a piece of old fuel hose. Remove needle and fuel inlet hose and blow back from needle to outlet.
Hold throttle and when you turn on brush, move throttle to wide open position. If it stalls, it is not getting fuel.
No leak at the carburetor mounting, all tight with good gaskets?