The 42A707 was a great engine and is well worth maintaining.

The carburetor on this engine has a built in fuel pump. Negative Pressure pulses from the crankcase are directed to the fuel pump to pump the fuel from the tank. After years of service, the diaphram may dry out, crack, and allow some fuel to be drawn into the crankcase. This would occur when the engine is running.

Another source of the fuel may be a leaking needle & seat in the carburetor. This may occur on a gravity feed fuel system when the engine is not running. The same thing will occur if there is a crack in the carburetor body.

To correct, the complete carburetor should be renewed. This is accomplished by removing, cleaning, inspecting, repairing the carburetor. A new carburetor kit contains the needle and seat ---- and the new fuel pump parts. When this repair is completed, install a new fuel filter and the fuel line between the fuel filter and the carburetor. Inspect the fuel pulse line and install clamps over the fittings.

To prevent other engine problems from developing, remove the sheetmetal from the cylinders for cleaning. If the cooling fins are plugged with grass, the engine will overheat and cause damage to the valve seats.