1. Check air filter. Clean/replace if necessary. Check or service air filter every 25 hours. Paper filters must be replaced. Foam filters may be washed out in hot soapy water. Squeeze dry and re oil with engine oil. Squeeze out excess oil.
2. Check spark plug. Look for excessive carbon deposits on the electrode. Clean, or replace with a new identical plug.
3. Carburetor may be out of adjustment. Screw in the high speed screw (bottom of carburetor) in until finger tight. Then:
IF Tecumseh, back out the screw 1-1/2 times.
IF Briggs and Stratton, back out screw 1-1/2 times (single cylinder)
IF Kohler, back screw out 1-1/2 times (single cylinder)
Adjust the idle screw (located on the side of carburetor) by screwing it in until finger tight and then:
IF Tecumseh, back out screw 1 time.
IF Briggs and Stratton, back out screw 1 time. (single cylinder)
IF Kohler, back srew out 1 time. (single cylinder)
4. Bad fuel. Replace with fresh, mid-grade automotive fuel.
5. Exhaust port clogged or restricted. 2-Cylces only. Remove the muffler and pull the engine over until the piston skirt blocks the exhaust port. Scrape away the carbon with a wooden dowel or somthing soft. **WARNING: YOU CANNOT SCATCH THE PISTON SKIRT. IF YOU DO, CYLINDER DAMAGE MAY OCCUR FROM THE SCAR ON THE SKIRT. THIS WILL REDUCE COMPRESSION, THUS MAKING THE ENGINE HARD TO START OR RUN PROPERLY.** Check the muffler for blockage and remove carbon from it.