AboutDavid R -GlobalTek LLC Expertise Small Air Cooled Engines and applications including Twin Cylinders. A specialist in the Chinese Engine-- i e LIFAN, LONCIN, ZONGSHEN, RATO, LCT, YAMAKOYO, DUCAR, GREYHOUND, (Honda Engine COPY) area. Have personally been to Chinese Engine factories several times Former Day to Day job is in application engineering of 4 cycle Engines. Evaulation, testing and failure diagnosis of Chinese Engines,Briggs and Stratton and Kohler engines daily. In other words I do this everyday.
Experience 30 Years in OPE industry. Briggs and Stratton Master Service Tech, Master Parts Pro. Former owner of OPE dealership servicing and selling Honda, MTD, Murray, Husqvarna, Toro, Lawnboy, Shindaiwa, Briggs and Stratton, Kohler, and Tecumseh. Previous job as trainer for engine manufacturer performing service training for companies like SEARS, HOME DEPOT, LOWES, TSC, etc. Instructor for Technical College.
Education/Credentials Vo Tech Training 1981, Husqvarna Factory Training, Briggs and Stratton Factory Service School(s) Tecumseh Factory Training, Shindaiwa Factory Training, MTD, Hydrogear, Toro, Lawnboy update schools. To many to list in the past 30 years.
Question I have a Murray 22" side discharge mower where the engine keep revving up and down, up and down every few seconds. sometimes a puff of smoke comes out when it's revving back up. I've checked the oil and tried giving it new gas with a carburetor cleaning additive. I changed the plug fairly recently but when i pulled it out again it was kind of greasy/oily on on the threading and near where it fires. the engine is a Briggs and Stratton 10A902. Any advice? is it the carburetor?
Answer the condition you describe is known as "hunting and surging" It is most likely your carb. Make sure your air filter is clean. Remove it and test the engine to see if it makes any difference. I speculate your high speed nozzle in the carb is gummed up. There is a slim chance one of the vents are plugged in the carb to. Just for the fun of it, loosen your fuel cap and test to see if the problem goes away. If it does its a bad fuel cap vent and you will need to replace the cap.
