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Gearing and Transmission Ratios?????

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I've been looking for transmission ratios on the CRF450R and found a few posts on here with the ratios. so far I have found:

the crf ratios:

1.800 (27/15)

1.470 (25/17)

1.235 (21/17)

1.050 (21/20)

0.909 (20/22)

Now my question is, since second gear is a ratio of 1.470 which is .33 taller than first gear, with the ratio 1.800. Can I compensate my final drive sprockets .33 to make the same ratio?

What I'm wanting to do is have the same holeshot power in second gear that the bike now is producing in first gear.

example. If my current gearing is 13/49 (a ratio of 3.76) on the final drive sprockets, should I change to a 12/49 (a ratio of 4.08 which is approximatly the difference of .33, the same difference of the 1.800 of 1st gear in the transmission, to 1.470 of second gear in the transmission) to make the ground speed in second the same as it would be in first.....holy crap! does anybody understand that?

I want my second gear ground speed to be the same as my first gear ground speed now.

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Your just going to loose that much top speed if you do so! What do you do mostly MX or offroad? If its tight trails you will be fine until you hit the loggin rd. If its MX you will find you are shifting more and possibly running out of gear on the longer tracks etc. Just my thoughts.

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The difference between 1st and second is 22.4%. 3.76*1.224=4.6. To get a ratio roughly 4.6 you need the values listed above.


110/90-19 tire

enter the values you have and it will compute for you. Don't forget, you have to take redline (11,200?) and divide by the primary reduction (2.739) to get the max tranny speed (4089) for the math to come out right for speed.

You will reduce the overall top speed to 76MPH from 93.

also, this is with 0% tire slip and 0% clutch slip.

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