If it will burn off the prime and then die, you have a fuel supply problem.
If it's the carb-on-the-tank type engine, replace the diaphragm.
If it's the Quantum type (air filter and carb on the side of the engine), remove the float chamber, and check the main jet is clear. Carb will need to come off the engine for access.
phil_saunders@bigfoot.com
Phil Saunders, June 2008