Serowbot wrote on 07/24/14 at 17:54:45:Not actually more top speed... because our bike don't make enough power to redline the stock 5th gear... ('cept maybe Dave's bike,... with an overbore, carb, and cam)...
Serowbot: I made a single high speed attempt on my bike just once to see if I could do the "TON". I have the 18" rear wheel with the 130/70-18 tire, and according to your chart the bike should redline at 102.8 mph in 5th gear. My Trailtech Vapor is pretty accurate - and the max speed I recorded was 101.1, and it just seemed to stop accelerating at that speed....I had reached my terminal velocity.
So.....my modified engine in the Cafe' bike with me all tucked in......was able to come darn close to reaching the redline in high gear. There is no way that a stock bike (even in excellent health) could obtain the rpm redline in 5th....unless a tailwind and a large downhill was involved. (The stock speedo does not read real accurate...so a 100 mph reading doesn't mean you are really going 100 mph.)
Since that time I installed a larger front pulley and smaller back pulley, and my rpm's have dropped significantly. Where a stock bike at 70 mph would be turning 4,676 rpm - my bike is going 3,892 rpm. And it is true that I can no longer reach my top speed in 5th gear, somewhere around 85 it just stops pulling. If I want to go faster I have to shift down to 4th.....5th gear is now a cruising gear, and I only shift into that gear when I am above 60 mph.
I like my new tall gearing. It works well on my light bike - but would not be good for a bike with a windshield, bags or a large rider.
So.....higher gearing does not result in more speed - but does result in lower engine rpm at cruising speed.
Dave
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