85' 250r cylinder/sleeve questions -gurus help please

[3wheelrider]

Well,-rebuilding a top end 250r for someone. Was rebuilt recently just before he bought it. Now stopped running. Checked compression -felt low and it was (110!). Pulled the cylinder off and its scarred/charred some along the front &stuck rings). Piston to wall clearance is alot! . Measured piston- its a 72mm! Isnt this the last bore size? Sleeve thickness is at 6mm. Dont have a inside mic. to measure the cylinder i.d.- It may have been resleeved/not positive. But I dont see a casting # on the bottom on the sleeve. Shouldnt there be a 85' stamped on all original sleeves? Also the top of the sleeve where it meets the cylinder has 2 small spots where aluminum flaked away some (during resleeving?). My real question is can this cyl.be bored out more or not? Whats the limit?- :wondering

[Billy Golightly]

72mm is definitely a big bore sleeve. Probably an LA Sleeve "295" kit. Could you get some pictures of the aluminum "flaking"? Scarring and seizure on the piston is more likely than not from too tight of clearance, not too much. Pics will help :)

[3wheelrider]

Billy,-295 sleeve huh?...-Now it makes sense since there is so much sleeve left!.... I was wrong about the aluminum jug flaking off at the sleeve- the sleeve is actually whats flaked/chipped away just slightly on the outer edge where it meets the jug. Water appeared to be trying to work itself past the gasket & in the cyl. but didnt appear too yet. (rust stains on the 2 spots show how far water made it). The piston to wall clearance seems whole lot.Rings were really stuck. No deep scratches on the cyl.. The front edge of the piston is well rounded off & peppered, piston side facing exhaust is well worn/charred as flame/heat traveled down the side.(burning off any lubrication). Top of piston & head are barely peppered. I believe he ran it with the fuel off -doh! Also. they used the trx steel gasket! (Not a big bore headgasket).Oh yeah, port edges werent chamfered well either.= Multiple issues besides clearance. I'll try & gets some pics on here somehow-not that good with computers/technology.(I have yet to show my bikes too).
Billy,its 295cc at the last bore right? Whats the cc's at 72mm? (rough est.)? (short rod/unported/stock head)? How hard is it to get the piston? Cant really find em.' Any other input greatly appreciated.

[Billy Golightly]

What your describing sounds like a lean out condition (Sandblasted side of the piston on the exhaust side) from either an air leak or inadequate jetting. Leaning it out with a lack of fuel could do it too. It sounds like you've figured out most of the problems. Too small of head gasket that protruded into the combustion chamber, unchamfered (or poorly) ports.

I think those 295 kits start at 72mm and end up at 74? I can't remember to be honest. You might try a powersports/offroad catalog at www.wiseco.com. The piston should be setup for the earlier short rod style wrist pin location.

[ceaserthethird]

It's probable they didn't resurface the cylinder & head, Must be checked and done when resleeved.

Find a good local 2 stroke Service shop, or send it out to one of the Big company's...

POST some Pictures when you get a chance.