What's wrong with turning off the lawn mower when refueling? Carburetors and valves have been checked, and so have new ones.

What kind of gasoline engine is it? Two strokes? This model may cause this phenomenon when the exhaust pipe is seriously blocked. The small throttle can barely breathe, and the large throttle will endlessly discharge exhaust gas and suffocate.

Generally, this phenomenon is very similar to the decline of the main oil needle of a four-stroke carburetor. If it is a carburetor with rotary valve throttle, the oil level may be too low. This phenomenon is that there is only idle speed, and adding a little throttle means that the mixed steam is too dilute to stall.

In addition, you should also pay attention to the fact that the fuel tank cover should not be too dead, and the gasoline cannot flow into the carburetor smoothly. This phenomenon is that you can add a slightly larger throttle for a while and turn it off after a while.