I have 87 lt500r motor siezed up. I bought it from a guy who claimed he rebuilt the top and bottom end. while riding last night motor seized up. pulled cylinder off looks like piston was hitting the head. At this point I have all covers off (clutch/stator/head/cylinder). Down to the case sitting in the frame. From what I can tell he was telling the truth.

Seals look new, hot rod connecting rod, markings on rod ck 155. weisco piston no real carbon build up, can even make out the bore size on top of piston (87.00) Coll head dome marked 62 on side.

When I removed the cylinder from the case their was no plate. So I dont think it was stroked if you even can with this motor. When I spun the crank around no sounds of bearing grinding. Felt around in side the case no scratches or gouges that I could feel. I did about as good of a inspection that I can do with out spliting the case.

All that said have a fairly new rebuilt motor that failed because piston was hitting the head. My question is why would the piston hit the head and what can I do to fix it? Any Ideas would be much appreciated.

 

Does the piston stop flush with the top of the cyl.?

 

not sure the motor was seized up piston mid was stuck in cylinder. Marks on top of piston and bottom of dome. Would extra gaskets solve problem or is it something else causing this issue?

 

I kind of think the piston touched the head because it seized, rather than it seized because it touched. You would have heard it knocking if the piston was touching before it seized. Did you get the piston out of the jug? Rings intact? If not, the marks may have been the stuff (bits of ring) being trapped between the piston and head.

As a long shot, if your con-rod bearing or even possibly the crank bearing goes, it could allow the piston to travel enough to contact the head...

 

Connecting rod bearing went. the guy I got the bike from had no f-ing idea what he was doing. This should be a lesson to all. If you dont no what your doing have a pro do it, not even 20 hours on motor and it has to be torn down again.
what pisses me of the most is for a couple hundred dollars more it would have been done right the first time by some one who knew what they were doing. My fault for not asking who did the work!!!!!!!

Thanks for all the help will keep you updated after I have my motor guy split the case and see whats what.