Well actually, it is starting to make sense now. You slowed the hot engine and it stalls with a stuck valve. This keeps the engine from turning over easily but you took care of that with a pipe wrench. Now you have a bent push rod OR a broken rocker arm. So if you remove the valve cover and find that to be the case, why did the valve stick OR the valve guide may have worked up to where the valve keeper hit it. Either way, you need to check the cooling shroud for obstruction, the most common cause is overheating due to plugged heating shroud. Some people say that Ethanol fuel is causing this but I have no experience with that happening. IF the valve guide has worked loose, B&S says there is no fix except a new head. Well I have a fix. A stuck valve you can fix and buy a new push rod or rocker arm. Let us know what you find. Walt Conner

Yoou didn't state what tractor you had, but I think if you look in the owners manual, it'll tell you to turn off the engine at higher speed. Thee carb has a fuel shut off solenoid that blocks the Main Jet when the key is turned off. The engine is supposed to keep turning over for a few seconds to "purge" fuel vapors from the HOT exhaust system to prevent after fire. Back fire is through the carb, BTW. What I would do, is put a strong dose of carb cleaner in the fuel and see if that might clean up a varnished Main Jet. A lot of people like Sea Foam. EPA Mandates require that these run on the lean side because of emissions regulations. There's really not much "wiggle room", if the jet gets slightly restricted, because it's aalready on the ragged edge of being too lean. Also- Check carb/intake mounting bolts.gaskets. A vacuum leak would also lean out the fuel mix.

To start with, you should be able to get flow from the line out of the tank. Remove the fuel line from pump and let it lower than the fuel tank. The fuel should run out. Catch some in a pan to confirm your cleaning job. You didn't say what equipment it is in. If the line is drawing through the top of the fuel tank, a little suction will initiate the flow. If it isn't flowing you are dealing w/ an obstruction, a plugged vent or a missing pick up tube in the tank (if a top draw). That should get you started. A bit about these fuel pumps. They are not super pumps. Their purpose is to meet fuel demand. If you put a test line out of the pump and temporarily run the engine with some carb spray into the air horn- how much is it pumping? Lines that may be deteriorating or ends that don't seal well greatly affect operation. Beyond that, some set ups will barely leave a layer of fuel in the filter and that can be misleading. They also need a good seal at the impulse hose ends and the engine must not have seal or internal issues to produce vacuum.

Or could it be a faulty fuel pump allowing fuel to leak into the crank case through the dip stick tube?