you need to check your valve clearance every 6 months or 160hrs by yamaha specs. the specs are in the book. i would just use some of the good fuel injector cleaner from the auto parts store. not the cheap stuff, but the more expensive stuff. put in a new spark plug too. these things like to foul plugs if you hit the gas before they are warmed up. or your idle could need adjusted, but if it idles ok once its warm then don't worry about it.