Engine won't rev
 

Bought the kids a new to us total 125 atv. It runs, but took the family out yesterday and ran into issues. It doesn't seem to reach top rpms. It wouldn't climb hills that it should have the other kids atv climbed them with no problem and it is an 80cc. Where do I need to start? Clutch?

Sounds like could be clutch related. Don't know if the larger machines have the cvt or the plate style and centrifugal clutches.

Thanks , I figured it was either something in the clutches or possibly the cam. Supposedly the guy I got it from had not worked on it. So I was hoping it is the clutches.