I was surfing for alternative engines to use on a motorized bicycle. Mopeds! Mopedarmy has a LOT of information, and an excellent photo gallery. That is the source of this information. IMO, it's generally better to use a power unit that parts are most likely to be available for... yet this is no guearantee ! The mopedarmy photo gallery listed over 130 brands contributed. Out of the volunteered pics, I picked out these as the heavy hitters. These are from riders who chose to post pics of their bikes, which is not a scientific method of determining availability of parts, but it might be an indication? Puch 984 tomos 580 honda 559 motobecane 442 mobylette 206 vespa 407 garelli 348 peugeot 343 batavus 272 yamaha 184 sachs 170 solex 151 jawa 126 sparta 116 suzuki 110 kreidler 101 It's easy to guess where best availability might be... Most have pedals, most are in the 50cc class, and many have a variator and/or centrifugal clutch. Some have fabulous body and fender styles, others are simply bicycles. Most are step-thru frames, yet some are motorcycles. I have never heard of many of the brands mentioned, and presume any number of them were produced by a larger company and badged. Sure hope this is helpful if someone might be making a decision. Best rc .