Looking at your one picture, I see a black wire coming from under the flywheel. This is a points type ignition on your motor. Pop the muffler off and see how many rings are on the piston. 1 ring is a 35cc. 2 rings is a 40cc. They look the same. Yours has an aluminum prop hub which would not be on an earlier engine as they were steel. Could have been changed though. Bennettbuilt.com has an exploded parts diagram for these engines. I have both the 35 and 40cc engines. Good runeers just a little heavy.