Hello people,

I'm rebuilding my motorcycle engine, and have a question. Should I reassemble my piston and cylinder dry to seat the rings better, or is this a myth?

Hmm.

It won't do any harm to smear some engine oil on the cylinder walls prior to assembly. It is piston scuff you will be trying to avoid, especially if it is 2-stoke.

The bottom scraper ring is designed to keep excess oil away from the rings during normal operation. If your engine has a scraper ring. Also the combustion process will burn of any oil above the top ring.

Most builders don't start the engine straight from assembly anyway, they turn the engine with no plugs on the starter until the oil pressure is up to normal. This lubricates the engine in the normal way.

if it is a road going engine it probably makes little or no difference. May not make any difference anyway.

We used to use STP but that was prior to the 20 min, high load cycle, break-in theory.

Reassemble your piston and cylinder dry is not a myth, it is downright stupid. Of course you need to lubricate your piston and rings.

Perhaps you are confusing clutch plates and the piston. There are mechanics who think that clutch plates can be put in dry. We disagree. You should lubricate your clutch plates also.