Each of those should have their own article. I may try to get that done this weekend.
I learned to be a mechanic on all of these. The '51 Chevy had a babbited motor that we rebuilt at least twice before we put a full bearing motor in it. I've actually poured babbit material in my career. (I was probably 12). My Dad gave me the pickup in self defense after I wrecked his newest Chev (a 62).
I overhauled the motor on that Yammie the first winter I had it. I took 8th grade shop class specifically because Mr. Iksic (the teacher) told me I could. I missed the leather craft part of the class. It was worth it. I got over 30,000 miles out of that little 2 stroke and when I finally considered it deceased I used the wheels to build a welder cart. Somewhere I'm guessing that the yammie lives on in somebody's shop.
Did well with the Yamaha! That's a lot of miles. I agree, you should do a post or two Tom.