This is a common complaint we hear.
“My mower starts and runs, but as soon as I start to mow, the engine dies.”
There are several reasons this could be happening. The most common issue is fuel related; a person has been running lower grade fuel in their mower (meaning it contains ethanol) and it has finally gummed up the carburetor. The only way to fix this is either to install a carburetor rebuild kit or to replace the carburetor (honestly replacing a carburetor is sometimes the less expensive route).
Although we say it over and over, people simply don’t seem to listen. In small engines, it is necessary to use the highest octane fuel available along with a fuel stabilizer or if you are lucky and can find it, use ethanol free fuel. However, there are a few other issues that can cause this complaint.
If this is an engine on a push or self propelled mower, it is possible that either the governor or the carburetor are adjusted incorrectly. This doesn’t happen often, but it does happen. Unfortunately with the new EPA regulations, most carburetors can only be adjusted by a certified mechanic. The tools necessary aren’t available to the general public. Governor adjustments can be tricky as well. If you have some experience with small engines, it is possible to do these adjustments yourself, but honestly this also should go to a small engine mechanic.
If the engine that is bogging down is on a riding mower, more issues are available to address.
Some customers complain that the engine dies as soon as they engage their PTO clutch. PTO clutches can go bad, needing replacement.
If the engine is a twin cylinder, it will have two magneto coils to run it. If only one coil is firing, you might not notice it when you simply start your mower. However once the mower has the clutch engaged, it will die if only one coil is functioning. There simply isn’t enough power to run the engine at the correct RPM’s to cut grass. The best way to test this is with a spark tester; being sure to test both coils.