1983 atc 259r rus good but loses power when warmed up

[atc250extreme]

looking for a little help here my 83 atc250r starts,runs good untill the engine warms up then the wheeler loses power eventually stalling out and wont start untill has cooled down again,also acts like compression decreases at runningtemp.I know the engine needs a rebuild being that the parts are all still original to 83 including the reeds...was wondering if the reeds or jetting could cause this problem? or if its just the piston and ringswith a rich setting would cause these issues but i havent got any additional smoke out the exaust

also i have looked everywere for a gearshift lever for the trike if anyone knows of any around or possibly has one for sale let me know.

[thestud25]

I think you answered your own question. Needs a top end rebuild.