It should say somewhere on the side of the cylinder what size the engine is. For example, if it's a 90 it will say 90cc or maybe 82cc or something like that. I would use Honda GN4 10W-40 oil. If you can tell me the 10th digit (letter or number) of the VIN number, I can tell you what year it is. The VIN number should be stamped on the front of the frame somewhere.