Any one know any thing about putting a late model cr 250 engine in a 85-86 250r atc.
Such as does it fit right in or how much modification does it require?

stick with the 250 atc u can loads of power out of it. i have a 88 250r and im pushing like 68 h.p out of it. this is what i did to mine, go full porting on it and make sure u get somone who knows how to really port cause theres lots of fakers out there and good porting will give alot more power.next buy some real good race reeds. i went with the esr 2000 reeds.after get a better carb like a 36 mm and use like a 185 main jet.next get a real good exaust. i went with the esr trx5 pipe. also once its all togther make sure u break it in properly cause if u do so that more power to the rear wheels. theres many diffrent options u can go. u can even go with esr big cylinder kits that give crazy power and u can even make it a stoker, skies the limit or walet which ever. the set up i gave u cost me about 1000 dollors and its still very reliabe and every very fast. im pleased with my set up

check this website out. in my opinion they make the best honda 2 stroke parts

http://www.esr250.com/