0 ATV AnswerMan Tackles ATV and UTV Technical Questions

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Can’t Get Enough RPMHello, I have a 2004 arctic cat 500 auto 4x4 ATV. It has the carb with electric choke but is stock equipment, must be year change. Starts and idles great and runs fine for just a little while cold wide open and then starts sputtering and loss of power – runs all day long at 11 mph. Can’t go any faster or it will start sputtering as soon as you push throttle any farther. I have checked gas flow to carb, out of carb, by drain on bottom of bowl. I have cleaned carb found nothing, cleaned air filter, checked diodes in fuse box, pulled muffler off and it ran better but not great. It will pull a trailer full of logs all day but you have to keep RPM down to a certain spot and it will run perfect. It seems to act like a rev limiter problem to me but when you take it out for the first time after it is cooled off you can go full throttle for about 100 yards and after that it starts sputtering at that certain RPM and will keep doing it until you leave it to get cold again. Do you have any suggestions for me to try before I have to give up and hand it over to the service center and pay the big bucks that I don’t have at all right now at wood-cutting time? Thank you for your time.
HOPPER

It seems you have checked everything over. But what did you really find? Simply seeing fuel run into or out of a carburetor does not mean it is getting into the finer points of the carburetor like it really needs too. Also, since this unit uses the electric choke it is possible that the switch is bad or stuck possibly choking the engine partially or even fully. What does the spark plug look like in the machine? Reading the plug correctly will tell you how much fuel is getting into the cylinder. If it’s dark, burnt or sooty then you are actually flooding the engine and this could cause the problem you are describing. Other items could be low compression due to worn or stuck rings and a few other things that a dealer should be able to help you with. Check out these specific things before you turn to the dealer.