The Monza has always been a work in progress--when I first got it the bike looked great, but nearly everything was broken, or needed replacing. I keep fiddling with bits here, and there tuning as I learn. Lots of thanks to Paz for all the help and tutoring he's provided. I keep a fairly up to date build on the Puch-Avelo site: http://www.puch-avello.com/t3019-puch-monza-from-san-francisco-usa The engine is a Puch SL. Some folks think this to be a "Monza" engine, however it came on a large number of Euro Puch bikes including both mopeds, and small motos. The engine was available in many configurations from a two speed to a four speed. In this case it is a 4SL.