cr80 Help PLEASE!!!!

[2SmokeRacer]

i have a cr80 which i recently had resleeved due to a complete top end meltdown. I have rebuilt this thing twice in 2 weeks due to broken rings. Local shop is puzzled, can anyone please tell me what is going on maybe. all answers will be greatly appreciated... P.S. Both rings broke in same spot, but cylinder is as smooth as glass, with no knicks or snags. Thanks.

 

[whenfoxforks-ruled]

If it was me, I would have had it replated or just bought a new one. May have been the same price. There can be a lot of issues with sleeved 2 strokes, you have a big one.

 

[helio lucas]

where did it broke?
no two sroke cylinder is smooth as they generally have ports on the bore...

 

[rpm12505]

Ring gap correct? Ports chamfered?

 

[2SmokeRacer]

i didn't LITERALLY mean smooth as glass, of course it has ports. i just meant that there is absolutely no scars.

as for where the ring broke, yes it was at the gap, and i don't really know what chamfered ports are.??

 

[Matt90GT]

DId you have the company that did the sleeve supply you with a piston also? Most likely the piston is the incorrect size for the bore if you are having this much issue.

 

[whenfoxforks-ruled]

Come on, out with it, who sleeved it? He had to of fit the piston, maybe? They check it with the piston, and you get the rings to size? You did put it in the correct way?

 

[2SmokeRacer]

the machine shop instructor at a vocational school locally installed it, only person that would. the brand of the sleeve is LA sleeve, and all the porting looks exactly like stock, and he had to bore the sleeve to match a std. B piston. the sleeve was slightly smaller than stock bore, and i checked 2day and can't really find anything the ring could maybe snag on. One more thing, to be honest. when i first installed the new piston and ring and things, on the first few initial kicks, the ring stuck at about the same position on the piston as where it has been breaking. Then when the first ring broke, I slightly filed the ring groove, because it put a small burr in the alum. Should i have bought a new piston when i did this. BTW, i am very tedious at everything i do, so the ring shouldnt have stuck again. I just lost power and comp., and found on teardown. Sorry so long.

 

[helio lucas]

what i mean when i say the bore has ports in it was that more likely the ring get catch on a port...
if the piston was intalled backwards the ring peg would be at exhaust port (ring gap is to the inlet side) and if the sleeve is badly instaled, with a few degrees from centerline, the ring woul catch a tranfer port... this you could see looking at the ports to see if they match...
the ports should be chamfered as pointed before or the ring could break on passing one port
take a look :cool:
http://www.youtube.com/watch?v=bFkpxW4xHhA

could you post some pics?

 

[2SmokeRacer]

thanks for the vid...i think i will try this b/c that is exactly what i think is going on.. I am going to try to post pics, to see if u can find anything different for me. Pretty sure u are right tho.