Hi.

I have a problem with my ATV.
It accelerate fine, but when it reach about 24mph it kind of shooting from the exhaust, slows a little down, and then it does it again when it reach 24mph. It feels like it want to go faster.
I have another one, and full speed on that, is about 36mph.

I found some different manuals for the engine, and some says that the Main jet should be 82,5, another 85 and the last one 87.
I put a 86 main jet in it, the spark plug is a bit grey, but I'm not afraid about that.
I have change air filter, gear oil, 2 stroke oil, cleaned the carb and checked for any air leaks. But everything is fine.
Any ideas / solutions?? :-)

 

If it is a two stroke, check the exhaust system isn't partly blocked.

 

Shouldn't it solved itself, by running the ATV for a longer distance?

 

No. Sometimes they need burnt out. Sometimes there is a screen in the end of the exhaust that goos up also.
Also check to see that the vent on the gas cap is working.

 

I bought it 1 month ago and It didn't work at all, but it's looks so fine every were, and I doubt that it have been running many hours.
So I'm not sure, but don't think the exhaust should be faulty. When I changed the gasket, I didn't notice any huge coatings in it.
About the gas cab vent, there is none

 

It sounds like it is a fuel starvation issue. The cap needs to vent somehow. Try leaving the cap very loose and running it to eliminate that aspect.

 

Sorry. I meant that there is a hole in the gas cap, but the hose with vent is missing