worn piston

I have a 80 yamaha qt50. It runs, but very poorly. I took off the exauhst pipe and found the piston has scratches all over it. It is probably not getting proper compression because of this. What can be done to fix this? Can I just buy new rings or should I get the engine bored larger and get a larger piston? I dont want to spend much money because this thing is pretty old, I just want it to run ok. Any help would be great.

Re: worn piston

Check compression.. check everything..

see if oversized rings are available. Most times they are. Maybe the cylinder can be honed to remove the scratches and new rings fitted.

before you spend a dime, determine the extent of the damage. Measure how badly the cylinder and piston are worn. New standard size rings may be all thats needed.. But if f the damage was caused by a lack of lubrication, all the bearing surfaces in the engine, from main bearings to connecting rod ends may also be trashed.

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