Was out on the trails this weekend and things were running well when suddenly I noticed the engine would not slow down to idle or let me shift unless I turned off key and then adjusted shifter and started in gear. Not too safe, by the way. Anyway I got back to the house OK but can't find a reason that it is running fast. I start it up and it spins at anywhere from 3500-4000 RPM. I did not find an air leak or other obvious problem. It is the 4 stroke with Mikuni carb. Could there be a problem with the diaphragm in the carb?

Any thoughts or help is appreciated.

 

First thing is make sure you have only 1/8" slack at the throttle lever. The cable adjuster is right down from the throttle housing if it needs adjusting. Second there is an idle adjuster at the bottom of the carb.Item#25. Plus make sure the cable isn't binding causing the high idle. If this still doesn't help,could be a fuel supply problem with the pump or an internal carb problem.

 

Thanks for the feedback. I will check it out next opportunity, machines are at cottage so will have to wait until weekend.