250r piston not coming to the top.

[crazybuffalo]

Hey ive got an 86 R with big problem. in a feat of brilliance i bought a "cheater cylinder" off the internet. its got the cr250 sleeve and piston. the problem is it came with what is stamped as an 88 piston. as you know the 86 had the short rod, and when i put on the piston for the 88 style and put the cylinder on its coming up short like an 89 r piston on an 86 rod. I was going to order a piston for a regular 86 r, but i got to looking and the piston is 1.50 over, fine again, just find an 86 1.50 piston right? wrong, the 88 cr, as i just found out, has a stock bore of 66.4 where as the R is just 66. so that puts me in the need of an 86 style 1.90 over piston. Does anybody know where i could get a 86 1.90 piston or if the cr's from 86 used a different pin height like an R? i would just change over to a long rod crank, but its got a hot rods crank already in it, and i really didnt want to have to split the cases. any help would be greatly appreciated.

[Aceman]

If all else fails you can probably bore the cylinder out to a standard 86 size, if you can't find a piston that is.

[Dave83]

Niks made some odd pistons for the short rod motor.You may have to bore it to 68mm to get a piston that will work.You need to take a pair of calipers to the cylinder and see what you really have.I lifted this from Nacs site
http://store.nexternal.com/shared/StoreFront/default.asp?CS=nacs&StoreType=BtoC&Count1=281597316&Count2=198737740

[crazybuffalo]

hey i thought of that (boring it to 68), but i was afraid that when they bore it they will try and smooth the edges off that go to the intake and the exhaust and screw up the port work on it. its been done by jc racing, ive been told that they do mostly crotch rocket motors for the aprilla bikes. i dont know tho. would you guess it would cause a problem there?(porting) thx for the replies btw.

[86 Quad R]

as mentioned i would measure the bore and see what it actually is. if you do end up having to bore the cylinder to a regular 85-86 trx size you should be ok on the porting as long as you get a reputable shop to do it. at that i would still check behind them and make sure that the port edges are radiused as they should be.