I can see some linkage from what looks like the base of the engine up to the carberator gentley moving up and down approx every 2 seconds. This in turn is effectiving the revs. If I force the linkage down, the engine cuts out. Up and it revs high. This happens both on engine idle and full throttle.

Ross, September 2010

this is a common issue with these engines and may be unsolvable
try the coils for even blue spark at the plugs

Geoff, March 2016

cleaning may help but the root problem is incorrect mixture setting or blocked jet. The fall in revs causes the governor to open up the throttle, the engine picks up speed with a surge reaches the upper rev limit set by the governor but as the mixture is unstable the engine speed falls again to repeat the cycle. Remove any idle or mixture control screws (counting the turns to remove so they can be replaced exactly in the same position). Check the air and fuel jets are clear.

vlad, October 2010

It sounds like your carb is dirty.you need to take it off and take it apart soak it in either carb cleaner or boil it in soapy water. If you use carb cleaner make sure not to get any rubber parts in it. they will swell up and won't work

hogdoctor, September 2010