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Discussion Starter #1
Hi all,

After mixed results in my last 2 fuel economy competition I am in need of taller gearing for my CBR250r. I won my first competition ( 135 mpg) but finished 3rd in my last one ( 133mpg). I'm currently running 15T/36T gearing. I've checked conventional sources and found that a 15T is the largest available. The CBR has plenty of torque to go taller but the sprocket selections are limited ( 15T front , 36T rear . Have any of you found a 16T sprocket that matches the splines of the CBR250r ? I don't mind doing some grinding to get the necessary clearance. Any help is appreciated.
many thanks
 

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Hey Vic!

Can't say I've seen anything that would help you, but do they publish any specs for the countershaft - diameter, splines, etc? I would think Honda would have used a similar countershaft on something, and maybe there are more options available.

Have you checked into rear sprockets? Are you planning to change both, or just the front if you can get it?
 

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Discussion Starter #3 (Edited by Moderator)
Hey Vic!

Can't say I've seen anything that would help you, but do they publish any specs for the countershaft - diameter, splines, etc? I would think Honda would have used a similar countershaft on something, and maybe there are more options available.

Have you checked into rear sprockets? Are you planning to change both, or just the front if you can get it?

Hi Jay, I changed the rear sprocket to a 36T which was the tallest available when I checked but will recheck now. I may also look at getting a taller rear tire.
thank you, Vic
 

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Hi Jay, I changed the rear sprocket to a 36T which was the tallest available when I checked but will recheck now. I may also look at getting a taller rear tire.
thank you, Vic
There are places that will custom-make rear sprockets. I didn't think it was crazy expensive.

Do you have the room to go smaller with the rear if you can't find a larger front?
 
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