Small Engines (Lawn Mowers, etc.): yamakoyo 5.5hp gasoline engine, gumout carb cleaner, ethanol gas

Question

yamakoyo 5.5hp gasolin   Yamakoyo 5.5hp gasoline engine is 5 months old and is mounted on a murray go kart.Starts fine but when taken off choke governor revs up & down continuosly.Have remove carb,sprayed w/Gumout carb cleaner,blew out,checked float, checked muffler for obstructions, changed the spark plug, adjusted the engine speed, changed the gas to no ethanol gas, changed the oil, etc.Acts same as originally rev up and down continuously. It will smooth out somewhat when choke held half open/closed. At wits end for answers.
Thanks,
Uthman

Answer
uthman

Check the settings for the governor springs,make sure that what ever holes the springs is attached to are the correct ones. One thing you can do is make sure the the governor spring is not stretched out or deformed in any way.Try moving the governor spring to a different hole,make sure you mark the old hole so if it gets worse you can set it back,try different holes if this doesn't help then you may still have carburetor problems with debris blocking a port.

Newer carbs probably have build up problems internally that are restricting fuel flow. Another reason a small engine could surge would include an air leak in the intake side of the engine. You could spray carb cleaner on the gaskets and intake when the engine is running. If there is a leak, the engine should rev up or bog down quickly when being sprayed. The governor system could also cause the engine to surge. The governing system usually uses an air vane with a few throttle linkages to control the amount of power being delivered to the vehicle. The engine power will be limited until the engine is being bogged down then the governor throttle will open to make more power. Go cart owners will often stiffen or shorten this spring to hold the throttle plate wide open to deliver the full power of the engine. The governing speed is a very touchy set up and should not be messed with unless your confident about what you are doing.