alright this is a bit of a story i traded my banshee for an 86 4trx250r and an 86 atc250r now the 4trx has some small tranny problems so i stuck the engine from the 86 atc250r in and its BAD!! its 20 mm. over it's been ported milled polished wiseco piston boysesnreeds&cage it was built by paul turnner but i want the 4trx engine back in it for what iv seen is fairly stock and im haveing the tranny rebuilt and im putting a new topend in too BUT..im going to really miss all the power im a huge quad nut so i do have many idea's of my own but id like to hear from you what i can do for the org 4trx engine that doesn't cost a ton of cash thanks

Why dont you take the ported jug from the atc motor and put it on the 250r motor??

its so simple...hey...hehe mmaann im a dumbass and i can punch it out another 10mm while im at it too some things are so simple they fly over your head like looking for your shoes when your wearing them hehe

first of all, you mean .020 and .010, not 20mm and 10mm. if you bored your R's cylinder out 20mm, all you'd have left is a pile of metal shavings.

simply boring your engine out a few overbores doesn't increase power, the real power is in porting, head mods, pipe selection, and the like.

ok im not going to fight with you about the boreing ...and i already know displacment is almost nothing without it being ported&polished and yes i know the porting will be off if i get carried away with boreing it but than that i have it covered thats already done by paul turnner so it would give me a few steps up in power and i have an fmf fatty gold series pipe which i love alot!! one of the best pipe's in the world for the r if you woods ride or race mx it'll be pretty cool

no offense, but unless you go substancially bigger (say 295 cc which requires your cylinder to be resleeved with a special sleeve) you won't notice an increase in power, all you'd be doing is wasting bore sizes.

what..your on drug's people do small bore job's all the time and notice power gain's you just gotta have the rest of the engine setup for that or it IS just a waste of bore's hey dill what kinda piston you think it's a choice beteewn wiseco pro lite or the pro x with the cooling hole's already drilled in it

OK this is a real stupid suggestion but why not just stick with the 86 ATC engine as it is the same as the 86 trx engine except the trx engines compression was lowered to help make it run a little cooler. And I do have to agree with Dill, you are not going to see a big power gain unless you resleeve it out to a 295.

well id do that but the 4trx engine is down for repair so im just going to rebuild it top to bottom and im rippin apart the quad anyways to put new bearing's and seal bushings etc in the frame and i need something to ride while im doing this or ill go nuts im a dirt junkie plus my carrier bearings are wasted and i have a dura blue axle im putting in so id have to take the rear apart anyways

sounds like a future parts doner.