I just noticed something whilst looking at the 4th picture of John's Yamaha. Look at the Primary Ratio on that thing! The front gear is tiny, while the clutch basket looks to be (appropriately) the size of a basketball! Looking at that, I imagine you could rev the bike up to nine grand and still watch each individual gear tooth in the transmission as it went around. Crazy.
I'm used to looking at Maico equipment, which has a much more mild ratio, resulting in a fast-spinning transmission. They did this so that the RPM in the transmission would be higher, and thus the torque would be lower, allowing them to use a clutch you might expect to see on a 100cc trail bike, rather than one of those big monsters you get on a CR or similar. That's why they could get away with such small cases; everything inside was small and fast.
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