who makes aftermarket bike transmission parts

[12oclocker]

I wanted to know exactly what gearing I had to gear a new 09 WR250X to make it exactly like my CRF250X in first gear, then I wanted to be able to calculate what the top speed would still be (estimate) here is what I did....

09 wr250x gear ratios (from service manual specs)

37/14 2.642 1st gear

29/16 1.813

29/22 1.318

26/25 1.040

24/27 0.888

22/28 0.786

78/25 3.120 primary reduction (crank)

42/13 3.231 final reduction (sprockets)

CRF250X gear ratios (from service manual specs)

65/18 3.611 primary reduction (crank)

54/14 3.857 Final Reduction (sprockets) [stock sprockets]

48/14 3.428 Final Reduction (sprockets) [hard to circle setup, but more speed)

48/12 4.0 Final Reduction (sprockets) [easy to circle, perfect setup)

Gear Ratios

1st 2.384 (31/13)

2nd 1.750 (28/16)

3rd 1.333 (28/21)

4th 1.041 (25/24)

5th 0.814 (22/27)

For my optimal setup, I found a final ratio of 34.434 for a 250cc engine was the optimal ratio for a typical supermoto wheel.

Final Ratio was calculated using....

"primary reduction" * "selected gear ratio (1st gear)" * "Final Reduction"

In order to obtain the closest possible ratio on the WR250X, I found I would need to regear the bike -1 +8, or (50/12 [4.166] for a final ratio of 34.346)

This reduces the wr250x top speed from 95mph (estimate) to about 73mph (estimate) though.

(stock final ratio 7.923 estimated top speed around 95)

(50/12 final ratio 10.218 estimated top speed around 73)

my CRF250X geared 48/14 could hit 75mph and had a final ratio of 10.077

my current optimal parking lot gearing has me at a final ratio of 11.757 and a safe top speed of around 58mph.

So now I'm up in the air about getting a WR250X, it'll still be faster than my current bike, but not by much.

Takegawa makes a 6 speed transmission kit for the CRF100's but I cant find any info on the CRF250's I wish someone made a aftermarket kit for the bigger CRF's, I'd like to either have 6 gears, or a custom lower 1st gear, or higher 5th gear. anyone know of anything out there that may exist?

[phugitive]

Yes the delema of gearing, low first gears for stunts and such and higher top gear so you don't get spanked on the street. After buying many sprockets and chains I have come to the conclusion that no gearing is perfect for every situation. Regear for fast take off get passed at top end, regear for top end trail 3/4 of race. The trick is to pick the best gear for a peticular situation or compromise and have a bike that is perfect for no situation but ok all around. Your quest is honorable.

[12oclocker]

I know, I've thought about having a machine shop custom make me a gear for the transmission, but who knows how well that would hold up, probably no where near as good as a stock one.

I'll probably just get the WR250X, and regear it, It'll at least hit 70's geared the way I like.

[Moto-Brian]

I know, I've thought about having a machine shop custom make me a gear for the transmission, but who knows how well that would hold up, probably no where near as good as a stock one.

I'll probably just get the WR250X, and regear it, It'll at least hit 70's geared the way I like.

Not a good idea... They'd have to get a certain type of hardened steel and such to work. You're looking at so damn much money in tooling and design to get it right that you'd be better off just buying the sprockets you need and slapping them on and off as you desire.

Just change the gearing and get a spare rear rim so you can swap them out for parking lot and street. Get two chains as the lengths will be different. You could change a chain and rear rim in under 10 minutes easily enough and be on your way...

[12oclocker]

I'd really like a supermoto I can hit the interstate to work, and stunt in the parking lot at work too, lol. I guess the WR250X is still the best bet for that even after regearing.