Small Engine Troubleshooting Problems? Ask a Mechanic Now.
If it ran ok before it sat then it is almost certainly a problem with old fuel varnish buildup clogging the jets and fuel passages in the carb. There is no cleaner that you can add to the fuel to remove the varnish. The carb will need to be disassembled, all components soaked in a commercial grade of carburetor cleaner, rinsed, blow dried, all passages and jets checked for restriction, reassembled with new O rings and load tested to confirm the operation of the unit.
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