Sprockets & rear tire size xr 650r????

CORAL'S BELLMAN

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Hi,
I have a XR 650R that I am planning on racing (200 miles), 50% of the course is sand and whoops, very technical, 50% has flat wide open roads, the bike has a stock engine, the only thing added to it are the fmf header, procircuit t4 pipe and jetting, the sprockets size are 15/45 and the rear tire size is 120/90-18, is that good enough or should I change some of that????????? THANX!!!
 
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Total Loss

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I'm running 15/48- fast enough for me.
120 rear is a must for the 650.
Make sure you use Bridgestone ultra heavy duty tubes.
Good luck.
 
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DRZ_Motorsports_119

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I run 15-47 uncorked XR650R with a PC T-4, whats the diference between:

*15-47
*15-48
*15-45

will like the opinion on the experts considering i have to buy new sprockets????

I do ride my 650 in Baja mostly rough technical stuff (mikes sky ranch type terrain), no high open speed like the desert, northern part of baja (tijuana,tecate,ensenada, NO desert).


Erick D.
 

Waldo

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I run 15-47 uncorked XR650R with a PC T-4, whats the diference between:

*15-47
*15-48
*15-45

Your current ratio is 15 X 47 = 3.13

Since your countershaft is the same in all three scenarios...The more teeth you have on the rear sprocket...the quicker you will accelerate. However, you will lose top end speed. If you are not doing high speed stuff...you could try a 48???

In general, if you change the countershaft sprocket by one tooth, it's like changing the rear sprocket by four.
 

troyharper

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Your current ratio is 15 X 47 = 3.13

Since your countershaft is the same in all three scenarios...The more teeth you have on the rear sprocket...the quicker you will accelerate. However, you will lose top end speed. If you are not doing high speed stuff...you could try a 48???

In general, if you change the countershaft sprocket by one tooth, it's like changing the rear sprocket by four.

or 3 :)
 
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