file the skirt of the piston so its slightly bevelled, finish with an oil stone for smoothness. The bevel edge causes oil to funnel inwards and push into the gap between the piston and bore. - Also make sure small end bore edges on the piston are not sharp either (aftermarket pistons are hopelessly unfinished)
You should also make sure the piston ring edges where they join together are not sharp as they can scratch the cylinder bore when the engine runs at normal temperature.
You should buy a bottle of a high quality 2 stroke oil and premix that in the fuel rather than using generic motor oil which will cause gumming. Correct 2 stroke ashless oil keeps everything very neat. - assemble piston assembly with a coating of 2 stroke oil for easy start.
