Sprokets.......agian.

[Dutch]

ok, i am getting a crf250r im at Least a month, im stoked. my friend has one, and im not real enthoosd about its top end speeds. its a little to slow for the flat vally. i want to mess with the sprokets to give a few miles perhour.
i dont know how smaller of a sproket i should go to give it a contiterable increas amount of speed. any input will do. and i would like to know(now that i thought about it) how long avridge a gas tank will last, say at pismo.

[mxracr121]

Originally Posted by Dutch

ok, i am getting a crf250r im at Least a month, im stoked. my friend has one, and im not real enthoosd about its top end speeds. its a little to slow for the flat vally. i want to mess with the sprokets to give a few miles perhour.
i dont know how smaller of a sproket i should go to give it a contiterable increas amount of speed. any input will do. and i would like to know(now that i thought about it) how long avridge a gas tank will last, say at pismo.

You should pay better attention in your English class.

[pjg351]

okay here is a maths formular and a sprocket chart that should help you work it out. see how you go.


SPROCKET MATH

There are only two basic equations for sprocket math: calculating the sprocket drive ratio and calculating the percentage change in sprocket ratios.

Calculating the sprocket drive ratio:

(Rear tooth count) / (front tooth count) = drive ratio

Example 1:
Bike ships stock with 47 tooth rear sprocket, 15 tooth front sprocket.
47 / 15 = 3.13333
So 3.13333 is the stock sprocket ratio.

Example 2:
You buy a 50 tooth rear sprocket and a 15 tooth front sprocket for the above bike.
50 / 15 = 3.33333
So 3.33333 is the new sprocket ratio.



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[crfjedi393]

We have two CRF250R's. I can't really answer the sprocket question. I prefer to stay stock at this point although my son went up to a 52 on his. 98% motocross riding and he LOVES the extra hit on the bottom. It made enough difference that I wouldn't go more than one tooth at a time when you change it.
As for how long a tank of gas will last? My longest X-country race this year was 1 hour 51 minutes. I was curious how much gas I had left. I drained 3 cups and quit because I knew I wouldn't race any longer than that during this series. So you can be sure a tank will last at least 2 hours.

[Dutch]

Originally Posted by mxracr121

You should pay better attention in your English class.

yeah, sorry i forgot to proof read it, i was to excited.

[Dutch]

That is a start, but i can't "spell" things out that clearly. You've given me a formula, which is great, but i can seem to figure out how drastic of an increase it is. well i guess the only way im going to know if i like what happens, is to go out and try it.

[pjg351]

The rule of thumb i work on is if you want more top end then go either 2 less teeth on the back or add one on the front. one on the front is about the same as 3 teeth on the back. i am not sure what honda' are stock but if they are 13/49 then go to a 13/47 or a 14/50 . just compare the ratios on the chart i posted. but if you get to far away from stock the bike will suffer either down low or up high. your choise!

[Dutch]

thanks, i know what im going to do now.