Does it have a Tecumseh engine? If so, tilt it up on the right-side wheels so the primer button is on the high side (never tilt it up with the carb on the low side). Take out the brass bolt on the bottom of the carb fuel bowl. Clean out all the holes in the bolt; 1) large hole across the bottom 2) large hole in center of bolt with a medium-sized orifice at the bottom 3) tiny angled bleed near the top of the threads, frequently missed in this operation. Use a soft steel wire out of a paper wire tie like from a loaf of bread or for trash bags 4) blow out all orifices with auto carb cleaner spray and check the tiny bleed again with the wire. Put the bolt back in and set the mower on all four wheels. If the fuel bowl leaks, tighten the bolt just 1/8 turn at a time until it stops. The mower should now run. You may have to do this every year or so. Use of STA-BIL in your gas all the time will help prevent mower fuel problems.

Hey guys - I just read through all these posting since I have the same issue. Just bought a used Yard General with the 20HP Vanguard. Cut the yard twice beautifully - starts like it should, runs like it should. The last time I let it run out of gas. Once I refilled, it started up (not without a little effort to get gas back to the pump I suppose). It only ran about 20 seconds till I engaged the blades, and she started stalling till finally died. Wouldn't start till I pulled the gas line going TO the filter, let it drain out of the filter, tried and it started right up, for 20 more seconds. Same issue - won't start. Here's the strange thing - I can hear and see a rhythmic squirting sound from the carb, and see pooled gas in the bottom that gets disturbed each time I hear the sound. Its like the fuel pump is squirting gas in - all while nothing is running and battery disconnected. Thought at first it was vapor lock - took off the cap, pulled on the diaphram there, thought it was fixed, but died again. Anyone got any ideas? If the fuel pump loses its prime, is there some special procedure to follow? Thanks in advance! Mike

ab26, if your engine has a "fuel solenoid" in the carb bowl, you should shut your engine off at high RPM by turning off the IGNITION SWITCH. The solenoid has a plunger valve that shuts off the flow of gasoline to the MAIN JET. The solenoid is used to prevent the phenomenon known as "afterfire" (which is what you heard). It works like this: If you shut off you engine by moving the throttle to the idle/off position, you kill the spark ignition but gasoline continues to be fed to the intake of the engine (because the solenoid is still energized). This fuel air mix is now just passing through the cylinder and out the exhaust valve without ever combusting in the cylinder. The exhaust pipe and muffler are saturated with extreme heat from use. So long as the fuel/air mix is passing through the exhaust system at a pretty high velocity....no "afterfire, or ignition" can occur because the mix is whisked through without being able to heat to the point of spontaneous ignition. BUT, as soon as the crankshaft and pistons stop moving......so does the fuel air mix and at that point the blazing hot surfaces in the exhaust system instantly raise the temperature of the mix to the point of spontaneous combustion and BANG is the result. Now, when you shut down your solenoid equipped engine at high RPM by turning off the IGNITION SWITCH, this is what happens: Turn key off, fuel solenoid closes depriving the engine of its main jet fuel. Engine immediately burns the last puff of fuel mix in the normal fashion (because the spark ignition is still firing the plugs). As the last of the gas is burned, the engine RPM sudenly dives toward zero, all the while the engine is being purged and ventilated by the air that continues to flow (minus fuel of course) through the engine and out the exhaust. Because fuel is absent, when the engine finally stops at zero RPM under these conditions, there can be no "afterfire" bang.

Walt, Thanks for the quick reply. A service manual would be great; I'll email you. It was the exhaust valve that was way out of spec, so much that the valve cap came off! This tractor has less than 100 hours on it. When I saw that, I checked the rockers, pushrods, studs, etc. I've re-checked to lash several times after running the mower to ensure it stayed within spec. I have the intake at .004" and the exhaust at .006". The only thing I haven't done while testing is the gasket around the valve cover. If this were a car I'd check the carb further, but there is nothing to adjust on these B&S engines. Furthermore, I notice the throttle linkage does not go all the way to the idle speed set screw at the lowest throttle setting. Could I have a governor issue? Just seems unlikely it happens to pop up at the same time, right? Best, Michael.