broken sleeve

[87250rxrider]

well, just 2 days ago, my R's engine seized( i shut it down right away when i heard a god aweful clunking noise). with the sound it made right before it seized i thought a tranny gear broke, but when i took the topend apart today i found that to be untrue. there are metal shavings and metal chunks all over the cylinder and piston. i thought the piston was seized but i took the cylinder off and the piston slipped right out. well, when i flipped the cylinder over and looked in a big piece of the sleeve was missing from the intake port on down on one side(part of sleeve that goes into the case). there is a nice hole in that side of the piston, the rod is pretty eaten up, and the crank is seized with all the metal from the sleeve in there. i have a 69mm bore with a wiseco piston, a duncan 4mm stroker crank, 4.5mm spacer plate(ports line up perfectly) 21cc dome, c-leigh(NPRD) MX ported cylinder with a mikuni 38mm TMX slide carb, Bills midrange pipe, etc. the motor was putting out about 190PSI. the jug was just honed(only about 1 hour on it) and i had the motor running slightly rich. i'm wondering what could have caused the sleeve to break like that. if anybody has any info, than please share anything that could help with me.
BTW, sorry for the long post, but i tried to include all info for your info.
thanks,
-Ryan

[XCredrider]

i dont know what would cause that but i've had that happen twice. I'm on my third cylinder and redid the whole motor and never have had the problem since. The guy that i got my cylinder from said that a lot of people that bore motors dont put clamps around the two ears to hold them from being stressed whole being bored and it can develop hairline cracks and can break. This is just something i was told hwho builds motors for L.A. sleeve so im taking his word for it. :macho

[87250rxrider]

thanks a lot for the reply...very helpful. i plan to have the cylinder resleeved by LA sleeve, with a 295 sleeve, port matching, etc... hopefully it'll be as fast if not faster than it was.