I have a 1996 2 stroke, 60 hp Yamaha that has a carb problem. At full throttle position, I can only get 4000 RPM. I tried running it with the carb cover off and spraying Gumout carb cleaner in the carb throats and when I spraye the top and middle carbs, the engine would stumble. However, when I sprayed the bottom carb, the engine would rev to 6000. As long as I continued to spray, it would hold the rpms. As soon as I stopped, the engine would drop back to 4000.
Any suggestions on how to clear up this problem? I am trying not to have to take the carbs off if possible.
Trying to clean a carb by spraying something into it does absolutely nothing except clean the bore. The problem is "inside" the carb and the proper way to fix the problem is to disassemble, thoroughly clean every nook, cranny and orfice. Then reassemble with a new kit. The problem you have is obviously with the lower carb. That cylinder is running lean and you will burn down the engine if you keep running it with a clogged carb.
If you're running the motor at 6,000RPM's on carb cleaner(which contains no oil/lubricant), you may destroy it. If your carbs need cleaning, then it's the internal jets that are plugged up and will require disassembly for cleaning. After you get the carbs cleaned, install a fuel/water separator on your fuel line to help eliminate most fuel related problems. Good luck and don't destroy your motor!