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The Puff.
Join Date: Sep 2007
Location: U.S. Navy
Posts: 1,290
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Motorcycle Top Speed Help!
I am installing a new engine in my CL175 and it has different gear ratios! My goal is to be able to go 65 MPH at a comfortable RPM.
The ratios: Initial/Primary 3.33 First 2.769 Second 1.882 Third 1.4 Fourth 1.13 Fifth .96 Front Sprocket 14 Rear Sprocket WE DECIDE! The rear wheel circumference is about 80in. I may be able to install a thicker rear wheel. The bike redline is 8,500 RPM. I have already done the calculations, but I want to double check. The original gear ratios were: The ratios: Initial/Primary 3.7 First 2.769 Second 1.882 Third 1.45 Fourth 1.173 Fifth 1 Sprocket 2.5 Redline 9,500 RPM
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'70 CT1B '11 GTS 300 Super |
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04-13-2011, 07:35 PM
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Registered
Join Date: Mar 2008
Location: Fla panhandle / Roaming in my motorhome
Posts: 4,332
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Sorry no help here on the gear ratio. Is that the smallest twin cyl engine that Honda sold here? How about some pics.
Cheers Richard |
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04-13-2011, 08:27 PM
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"Sprocket 2.5" ?
I'd suggest having the 'final' ratio pretty close to what the factory used. Not sure what you mean by comfortable RPM, I'm thinking to pull 65 you're going to have to have it zinging pretty good. I have an old 400 twin I don't like going much over 65 with for any extended time; too buzzy for me, though I'm sure it wouldn't bother the motor to do so. Jim
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down to jap bikes that run and a dead Norton |
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04-14-2011, 02:17 AM
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"The primary contribution of government to this world is to elicit, entrench, enable, and finally to codify the most destructive aspects of the human personality." Jeffrey Tucker |
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04-14-2011, 02:39 AM
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Registered
Join Date: May 2004
Location: Lake Cle Elum - Eastern WA.
Posts: 8,417
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Years ago, when I was road racing, I wrote a computer program in BASIC that allowed you to put in sprocket size, tire size, etc and get the rpm vs speed.
But from experience, just up one tooth on the countershaft sprocket, or 3 teeth smaller on the rear.......That will lower your rpm by up to 500 at 65 mph....If you make more drastic changes, you won't have the torque to overcome the wind resistance and be shifting down all the time. Shifting down defeats your purpose...G'luck
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Bob S. 73.5 911T 1969 911T Coo' pay (one owner) 1960 Mercedes 190SL 1962 XKE Roadster (sold) - 13 motorcycles |
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04-14-2011, 03:16 AM
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The Puff.
Join Date: Sep 2007
Location: U.S. Navy
Posts: 1,290
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I made a spreadsheet yesterday. The bike was rated at 81 MPH max. I matched the speed on my spreadsheet at redline for both engines. It turns out the stock sprockets were 14 and 35, and my new sprockets should be 14 and 36 to 37 depending on rear tire size.
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'70 CT1B '11 GTS 300 Super |
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04-14-2011, 01:08 PM
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the stable a few years ago
2013 
