My 1974 Aquabug outboard motor (bought as a Christmas gift for me by Mom & Dad waaay back then) is a 1.2 hp Tanaka powerhead. Still have it to this day and though it hasn't been run in about 40 years now, I figure a carb cleaning, new fuel lines and spark plug & she's good to go. In the early 80's, Sears sold a friction drive bike engine powered by this same engine. I bought a new one out of the box at a nearby Sears Surplus store, just for the powerhead, which matched my outboard.
Totally agree with your observation of how well built the Tanaka motors were. I believe my Sears Gamefisher 3.0 hp outboard is also a Tanaka motor. Over on the motorized bike forums, I've read how highly regarded those Robin-Subaru engines are.
Back when I started driving, my first CG ship saw me without my car, a 74 Camaro, thanks to the high insurance premiums NJ was ripping off from entry level drivers. So, what to do in 1977/78 but to buy a brand new AMF Roadmaster moped, powered by the 50cc 2 stroke McCulloch friction drive motor. That was a fun ride!