A very small piece of rust or dirt from the tank can sit between the float needle and its seat. The needle then cannot seal, and fuel runs through the overflow or floods the engine. A sharp tap on the float bowl side can free it.
Safety
- Fuel is flammable. Work outdoors, away from sparks and heat. Wipe up any fuel.
- Turn the fuel tap off before checking anything under the carburettor.
Steps
- Put a container under the overflow tube and open the fuel tap. If fuel drips from the tube, the needle is not sealing.
- Tap the carburettor body sharply with a plastic hammer or the plastic handle of a screwdriver. Do not use metal.
- Watch the overflow tube. If the dripping stops, the needle has seated.
- Run the engine and check again after a few minutes.
Check your work
- No fuel from the overflow tube with the tap on, and no fuel smell at the carburettor.
If it did not fix the problem
- If it still leaks after tapping, the needle or seat is worn or damaged. Fit a new pair as in Check and replace the carburettor needle valve and seat.
- Dirt that returns means the tank or the fuel filter needs cleaning. See Check the carburettor float and needle valve.
- Carburettor overflows.