i'm guessing the bearing size would be a 6203 or 17mmx40mm....if so then the open type using oil is good for 21k and the standard contact seal with grease for 12k rpm. if you're up to it then using a real seal is the right way to go. that some manufacturers of high end "made for RC" gas engines use work-arounds like sealed bearings and relying solely on glue to locate bearings does not make it good engineering practice....when these things go bad (and they do) they go really bad.