Horizontal cylinder one-speed engine (H1): Pre-1977 had radial cylinder fins, a 1960’s design. 1976-78 had square shaped fins, a mid-1970’s design, and natural aluminum “angular” side covers. Post-1978 had raised-letter matte black finish side covers.
Vertical cylinder two-speed engine (G2 and V2): The Gulpmatic and VIP models had an upright cylinder (spark plug pointing up). Most of the engine was different from the horizontal engine on the other models. The front motor mount was in the head. The exhaust header was screw-on, not flange bolt-on. The drive chain was still on the right, unlike most other mopeds.