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Trouble in atv paradise

Im working on a 2001 arctic cat 300. After it is started it will run fine for 5-20 sec. 5 sec at idle, and around 20 with more throttle, then it starts to stutter and sounds like a two stroke. If I open the throttle too much, it just dies on me. The interesting thing is that if I restart it, it will run fine for another 20 sec.

The trick I have found to get it running like it should, is to open the trottle very slowly over a period of as much as 5 minutes. After that it will run perfect! The air temperature is that of a typical norwegian summer, ie in the 60s. But it shouldnt take THAT long to warm up. lol

The engine is a four stroke, single cylinder, cv carb, electronic ignition. The carb is the keihin cvk32.

Does anyone have an idea what could cause this kind of problems? I have of course taken apart the carb, and cleaned it.

This sounds like a carb problem to me. I suspect the float in the car is part of the problem.

That makes sense. Why would it clear up though?

This is the carb:

I agree it’s probably the carburetor. The symptoms are classic of a too lean mixture. The engine won’t run properly until the engine heats enough to completely vaporize the fuel. This site gives a pretty good explanation of the Keihin CV series and some advice about working on them.

Low compression is another possibility. Do a compression test before you get too far down the road on other repairs.

Thanks for the help guys! I’ll have to check the float level again then I guess.

I hear that’s very important. I just dont understand why… In an atv the carb will be at an angle a lot of the time when driving in terrain. Does it not affect the mix, because the jets are in the middle of the bowl, where fuel level may not be altered that much by driving?

Do you have easy access to the main jet? I’d take it out and look to make sure nothing’s plugged up. May want to run a thin wire through it and spray some carb cleaner. Then play around with adjusting it in & out.

I havent had a chance to look at it again, but I will this weekend. Will hoisting up the front of the atv be way of possibly detecting a faulty float bowl level?