I don't see this discussion in any old posts, so can anyone comment on the approximate max RPMs we can comfortably subject a stock engine to for sustained highway drives? There are several posts on sprockets, ratios, and top speeds, but none that I see that tie them all together.
I'm asking because, per a recent post, I'm going to drop my gear ratio a little bit. I'm currently running the stock military sprockets (19, 43, 18, 42). Rear tire is 26-inch DIA. If my calcs are correct, RPMs = (337*GR*MPH)/Dia. So, the max speed I've hit before the bike really feels like everything might come loose is about 55-60. At 55mph, my RPMs should be just over 3,700 (that is, 337*5.28*55/26). Does that sound right to everyone?
If so, then it's pretty easy to calculate any reduction in RPMs at various speeds if you change teeth on any sprockets.
Flat out is the only way to ride these old slugs! At night time it's great to watch the exhaust side glowing red, and you can toast your bread at the same time!
