Piston Scoring?replacement question

I have a garelli rally sport with a badly scored piston. I showed it to my auto mechanics teacher and he said i don't need to replace the whole piston but just hone out the cylinder and get new rings.

Does he know what he is talking about or not?


Re: Piston Scoring?replacement question

measure the diffrence between the piston and the bore,if out of spec.you should bore.also if the piston is round or egg shaped

Re: Piston Scoring?replacement question

If the piston is still round and true and non of the ring journals are nicked or collapsed then you should be able to get away with a hone and ring job.

For the cost of a piston it's always worth replacing though.


Re: Piston Scoring?replacement question

This is true.But do you know what caused the scoring in the first place?Just out of curiosity,if I had access to the tools(I do),I would mic the piston and cylinder,and see what you come up with.Scoring of a piston or cylinder is usually an indication of insufficient lubrication,overheating,dirt getting into the cylinder or improper fit between the piston and cylinder in the first place.You might also check both rod bearings,and the rod itself,to make sure it's straight.I would recommend a new piston if the old one is even the slightest bit out of round.And if your engine has oil injection,I would get rid of it,and run premix.Jerry.

Re: Piston Scoring?replacement question

oh well the jackass old owner ran it with out an airbox with a 51 jet. The rod is nice and straight What do you think???

Re: Piston Scoring?replacement question

If it was run without an air filter,that explains the scoring.If the piston is still nice and round,you can sand it lightly,and reuse it,it's up to you.I don't know how much a new one costs.I'd still replace it if it's cheap.Jerry

Re: Piston Scoring?replacement question

The whole piston kit is about $40, and you can get it in standard, 1st and second overbore. If the scuffing is really light, you could do the hone and new rings and probablt do well. The rings are something like $10. If you don't have good compression after that, you can always get the piston and bore the cylinder.

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