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Rebore size/piston clearance will depend on the piston diameter and engine type. A split skirt piston tends to have less clearance. An air cooled engine tends to have more clearance.
It is important the boring operation leaves the bore one or two hundredths of a mm undersize and final finishing is done with a micrometer hone passed rapidly up and down the bore in order to leave a 120 degree crosshatched pattern, proven to be the most efficient for oil retention.
It takes at least 1000 miles for steel piston rings to properly bed in but 500 miles is sufficient for cast iron rings and it is important to use a low spec oil for the bedding in process - straight 30 or a proprietary running in oil.
Using a high spec oil from the start is likely to result in the piston rings taking an extraordinary amount of time to bed in - if ever!
Disassemble throttle clean and lube it. Disconnect the throttle cable at the bottom end and use some spray lube at the top end. Let gravity do the rest of the work until you see oil come out the bottom of the cables than reassemble everything.
Buy a spark-plug piston stop - only a few dollars/euros - any place that deals with scooters will sell them as there isn't an easy way to stop a scooter piston.
You screw it into the spark plug hole and slowly rotate the crank until the piston comes up against the stop.
To do the flywheel bolt up again, rotate it the other way and you can torque it up correctly (very important!!!)
which ring goes at the top
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