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Transmission ratios

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Has anyone been able to change the tranny ratios in the 250R? I have an 05 and would like to make it more enduro friendly getting close to the x ratios. While the x gears do not fit into an R case, I'm wondering if there is another solution. I find it hard to imagine that a full mx bike doesn't have choices in terms of transmission cogs.

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That would be one of the most effective ways to get the R to be better suited to slower single track type riding. One of the biggest differences between the two bikes is that first gear is slower and much more suited to slow speed tough stuff on the X. The easiest gear ratio changes would be the final drive or sprockets, but it would be possible to also put the X primary gears into the R which would slow down the speed. The second biggest difference between the two would be the spacing between gears. The R gearing has less difference between the gears. There is at least one or maybe two of gear ratios that both bikes have in common.

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I looked @ the OEM transmission parts for both bikes and the gears for the R version are 234x1-krn 670. The x part numbers are 234x1-ksc 670. I'm wondering if the gears can be interchanged....

The R has 30T, 16T, 28T, 20T, 29T, 22T, 27T, 24T and 25T and

The X has 31T, 16T, 28T, 21T, 28T, 24T, 25T, 27T and 22T

Edited by SVR6
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Not sure what part or gears you'd like to change, whether to just slow down first gear or change the whole sequence of ratio's. Both bikes have a second gear ratio of 1.750 but because of the difference in the primary and final drives it probably doesnt seem like it. I was just trying to say that if you wanted to slow down first gear and for that matter all the rest of the gears for technical, slow tough stuff changing the primary ratio should do that. BTW the X fourth gear ratio is the same as the R fifth gear ratio of 1.042. Alittle more trivia, the X then has an overdrive ratio of .815 for its fifth gear. But I agree that if you could pick and choose some of the gear ratios you could probably really get the bike suited to your own preferences within reason.:smirk:

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I'd like to slow down the first gear and speed up 5th gear. The R ratios are too tight for woods. The final gear - sprocket changes would shorten all gears which doesn't help the high end.

This may be way too much work plus I'm figuring out how to ride the crf250r at higher speeds anyway.

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I'd like to slow down the first gear and speed up 5th gear. The R ratios are too tight for woods. The final gear - sprocket changes would shorten all gears which doesn't help the high end.

This may be way too much work plus I'm figuring out how to ride the crf250r at higher speeds anyway.

Gears cannot be swapped between the R and the X, the splines are different and the shaft lengths are also. One option would be to buy an X bottom end and mount your top end to it. These are starting to show up on eBay and could be feasible.You could buy 1 without either side cover,kicker, stator and flywheel,as yours could be used. You would need the clutch basket from the X as the primary ratios and tooth pitch is different. The cases will mount into your frame with no mods other than the rear brake pedal.

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Most of your woods riding is in 2nd and 3rd anyway, sometimes 4th. I never use 1st unless I am leaving the parking lot. I have hit 5th in some transfer sections but not for long. If you were going to invest in this, I would recommend a rekluse clutch for you, instead.

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