Try Seafoam, you can get it at Walmart or any auto parts store, read the label and pour some in the oil, run the engine at idle for 15/20 minutes, drain the oil and replace the filter, you will find the oil you drained out will be BLACK, Seafoam works VERY well cleaning deposits from your engines guts. While your at it fill the tank with gas and add the Seafoam as directed on the can, it will clean you injectors/carbs, valves and pistons. I use it in everything I have, and know MANY people that do. I bought a 2001 Kawasaki Voyager XII (I have 3 of them now) it had set for God Knows how long and the carbs was in bad shape, it would only run on full choke and missed on 1 cyl when I got it, before I went through all the trouble of a carb rebuild, I did the Seafoam in the gas tank thing, ran the bike until cooling fan came on and shut it down at a high idle, let it soak over night and did it again for a couple days, now it runs smooth as silk and no carb rebuild. I also add some to the gas about every 6 fill ups just because. GREAT STUFF.