if its the kind of engine that has the gas tank bolted to the bottom of
the carb, the the rubber gasket between the tank and carb needs to be
replaced,. its called a carb diaphram.ive fixed many doing what yours is
doing .youll need the engine model and spec number stamped on the
sheetmetal covering the top of the motor to get it or just take the old
gasket with you to match up..lucas