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Old 12-03-2012, 05:52 AM   #1
TheRadBaron OP
Gnarly Adventurer
 
Joined: Jul 2010
Location: Central Illinois
Oddometer: 433
'66 Yamaha Twin Jet 100. 60mph=2240 RPM!?

I just brought home a barn fresh '66 Yamaha YL1, aka Twin Jet 100. It's a 100cc, 2-stroke twin cylinder. I can't find my camera at the moment so I can't post a picture. Anyway, the speedometer has a little legend that says "60mph=2240rpm".
How can this be? This seems to be impossibly tall gearing for a little, tiny, 2-stroker. For example, my '72 Yamaha R5 (350cc 2-stroke twin) is turning about 5,000rpm at 60. My CB350 is turning 6,000. Hell, my 125hp FJ1100 is turning about 4,000 at 60. I can't imagine how this little bike has enough juice to move the bike that fast at that low RPM. If you were to ask me how fast I would guess a 100cc 2-stroke would be spinning at 60mph, I'd say about 8,000. Not 2,240.
Not that it would do it, of course, but that would put the theoretical, geared, top speed of the YL1 somewhere in the neighborhood of 240mph.
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