carb problem here

Sometimes the gas cap doesn't vent properly. You can search the forum for remedies

The fuel delivery on these engines use a simple gravity feed system. Your engine could be starved of gas (like mine used to be) Check fuel flow by removing the fuel line from your carburetor and turning the gas on. Does any fuel dribble out? You only need a small trickle. If nothing comes out or only one drop at a time, then I recommend buying a new fuel valve from sickbikeparts.com for about $15. This solved my fuel problem with a huge increase in fuel flow and these guys always have my parts delivered in just two days! Now my bike doesn't bog out any more at full throttle because it is getting as much fuel as it can burn under any circumstance. Good luck, I hope one of our comments may help get you back on the road!

I just said this in another thread, but I'll say it here too. I rejetted and that took care of it. At high RPM there just wasn't enough fuel coming in through the carb, and it was drowning in air. Larger jet allowed more fuel, and a much better top end because of it.

I had an almost identical problem when I first bought my bike. I took apart the carb and there was a sliver of black plastic wedged where the float arm needle sets in to stop fuel. Pretty easy to check and it doesn't cost anything but time. Remove the carb, remove the bowl, and then remove the pin that holds in the float arm and check to see if there's any garbage stuck in that hole where the needle goes.