WB20XM
Engine lacks power:
Possible cause: Bad fuel; pump stored without treating or draining petrol, or refuel with bad petrol.

Drain the fuel tank and carburetor. Then refuel with fresh petrol.
Correction
Possible cause: Bad fuel; pump stored without treating or draining petrol, or refuel with bad petrol.
Drain the fuel tank and carburetor. Then refuel with fresh petrol.