1st time topend rebuild?

[Sammundo]

hi. ts185 has 55psi compression so im assuming the rings have gone. i have no real history on the bike and have never done a topend before so was just after some advise as to what to look for and what to replace. More specifically what to look for in terms of whether it needs a new piston or re-bore.
Any advise muchly appreciated

[Lozza]

Piston/rings/rebore.

[chrisdespo]

When contemplating a rebuild the most important thing in my mind is to check the engine out completely. check the bore for ovality, then check the lip onb the to of the bore my guess is at 55psi it is stuffed and needs a bore. if the cylender bore is round with no lip or scoring you may get away with rings only, I would rebore and fit new over sized piston genuine parts if available. i would also check the crank and make sure that there is no play in bearingsof the bottom end. there is nothing worse than , and i have seen people do this time and time again rebuild the top end and think that the bottom end will be fine, only to have it break a rod and rip the transfer ports out of the barrel or poke the rod through the cases. my reciepe for a two stroke is as follows

                         Piston
                         Rings
                         Gudgeon pin and Bearing and clips
                         Fresh crank and seals
                         Gaskets
                         Fresh cylender bore

Remember if there has been enough contamination to wear the bore to only have 55 psi comp then the crank will be as bad, as the air fuel and dirt all go through the bottom end to get to the combustion chamber.
hope this is of help