If you can get a piston you should be able to rebore, thats the sleeves biggest advantage over plating. I've never tried trans fluid some say it makes the gears notchy, if you use it you must use type F the GM stuff is too slippery for the clutch.With motor oil you're supposed to use bike rated stuff JASCO or something like that, its been tested for use with clutches, these are old spec car oils. I'm going to try Magnatec by Castrol its not rated for clutch use but I've always got it in stock and 10W 40 covers most bikes except maybe hot 4 strokes in summer.