17/18 KX250f gearing- curious about going down a tooth?

Create New Tag

4/4/2018 10:41 PM

Been thinking about how my bike might feel with a little bit taller gearing. Anyone ride a 17-18 and gone down to a 49? Ride mostly MX, pretty light dude (130ish before gear) and I just feel like maybe this bike would benefit from the taller gearing? Mostly just to drag out the top end power/over rev a little bit for big hits or when I don't shift on a short straight. I've got plenty of grunt out of corners so I'm not too worried about low end loss


4/5/2018 2:56 AM

Ive got an 09 kx250. So hopefully this input helps... im a heavy dude and j think it should have more top speed. Bottom is really good but it signs off so fast and i feeel like theres a ton of shifting compared to my 450. So yeah id say youd benefit.


4/5/2018 2:25 PM

Going from a 50 to a 49 is only a 2% gearing change. That means, at the same gear and RPM, you'll be going 2% faster. Or, in the same gear at the same speed, the motor will be spinning 2% slower.

Why do you feel like you need to lower the final drive ratio? Are you in between gears at the tracks you ride at? Do you feel like you have to shift too much?

For motocross, the stock final drive ratio should be as low as you need to go. If you're doing desert racing or GNCC, you may want to lower the final drive so that you can go faster.

I personally choose to go higher in the final drive if i feel like i'm between gears too often around the track.

That all having been said, you can get cheap steel rear sprockets for 20$ and try it out.


4/5/2018 4:16 PM

I rode a YZ450 with desert gearing on an MX track once and it was eye-opening. I could go so fast down the straights in 3rd that I felt like I was floating. The tradeoff is that the thing felt sluggish and slow in the turns, even in 1st gear. 1T taller gearing (smaller rear) will feel a little like that, to a lesser degree.


Braaapin' aint easy.

4/5/2018 5:02 PM

Oh I'm familiar with what a change in gearing does, I've just never gone lower than stock on my bikes. Always played around 1-2 teeth more, but I always noticed what feels like way more than a 2% difference in the way the power feels. I remember reading the reviews about the 17 before I got mine that a few of the test riders felt like it would benefit from going one tooth lower for the higher final drive. I don't find myself shifting too much or being in between gears, mostly just looking to stretch out the final drive a hair for when I don't want to shift or can't, like when I'm hitting a big table or triple in 3rd/4th. Sometimes I feel like it would give me those extra few feet I need to clear some obstacles if I could stretch it out just a bit more