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ok so im not too happy with the gearing on my 05 crf450x, i usually ride on a dry lake bed, and dirt roads. i like to go somewhat fast, but any way my top speed is about 80mph.....starts to cut out. it sounds like its whining out even at 65-70mph, while holding throttle at 3/4 - 7/8. ok so, i want to be able to do 60-65 at 1/2 throttle (this is all in 5th gear by the way). stock the sprockets are 13-51. would making the front a 14 do it??? and i dont want to loose much bottom end... i dont know what to do, anything would help.

thanks a lot

brian

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Ive dropped the rear down to 49 on mine, have`nt a clue what kind of speed its doing but there`s still loads of bottom end there

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49 with the stock front will push a little over 100mph. I had mine up to 80+ with the stock gearing and over 90 with a 50 in the back

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Over 100 Shady? Damn, you got rockets strapped to that thing? Stock, mine will maybe get to 75 wide open. 1 tooth in the back is not going to make more than 1 or 2 mph difference.

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hmm, i was wound out on pavement when i hit 85 with the stock sprocket. A solid 90 with the 50, so i would imagine close to 100 with a 49. But let it be known. These tires arent balanced and anything over 70 is shady at best

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not sure about top speed but I can say that 1 tooth in the front makes much more of a difference than 1 tooth in the rear.

You can go here to input all the data to find out the truth.

go to the "gearing calculator" on the page

http://www.4strokes.com/tech/

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hmm, i was wound out on pavement when i hit 85 with the stock sprocket. A solid 90 with the 50, so i would imagine close to 100 with a 49. But let it be known. These tires arent balanced and anything over 70 is shady at best

100? I don't think so. I have a 49 rear on mine. I think 90 +/- is about tops with that gearing. There is no way I can hit 100. I clocked against a KTM with a speedometer. I passed the KTM when it was doing 85. But, I was just easing past him and I was flat out - probably doing about 90.

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1 in front = 3 in back

On the X its 4 teeth not 3, do the math.

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I have always heard that going up one in the front is like going down 2 in the back.

I run 13/49 and it is a nice setup.

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You can use a differential equation to solve these sprocket dilemma's:

If you have a 14 front and want to go to a 13, and wonder what you would have to do to get the same result if you changed the rear instead:

13/14= 51/X

X= unknown rear sprocket size

cross multiply 14X51=714

13X=714 solve for X

714/13=54.92

you would need a 54.92 rear=55 teeth

Or you can just use a chart!

I changed from a 14 to 13 at KM, it was like adding 4 teeth to the rear:

It made all the difference in the world......

And that ladies is Alegebra 101 for today.......

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But you make up for it with your good looks....Hehehe

13/49 is half way to a 14 front-you have a 13.5 front if the rear was a 51

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I have two 05' X's. I just changed the rears to 48's. Left stock counter whatever that is. Better on top end but still could use some more. It would make the street riding a little better. Obviously I am doing more trails than street riding. Anyone have an idea of how much more I can change the front or back to gain more top end without losing critical climbing ability?

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That depends on what you think is "critical climbing ability. You are almost the same as a 14 front, 13 is stock. If you go to 14 front, you would be fairly tall in 1st gear.

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13 / 48 will get you to 90 mph. Thats a 6.2 % increase in speed over the stock gearing of 13/51.

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Just try a 14 front. They're dirt cheap and easy to install. You'll probally like it. If not, put the 13 back on and go 49 rear. Problem solved!!

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