I have an 88' 250 R, it has a 310 kit, and the motor is blue printed and balanced. The guy I bought it off of ran a few cross-country races with it and a lot of trail riding. I am slowly but surely setting it up for motocross. I just got my bead locks in and I was curious what size front and rear sprockets I should run. right now I am running stock gearing, which I think is 13-38 but I maybe wrong, I know its a 13 on the front. Any help is greatly appreciated!

 

If you're planning on running 18" rear tires I'd go to a 14 front.

Hope this helps,

 

I run 13/38 gears with 18's and love it for mx.

 

I have a 330 kit on my R. I found that the 13-38 gearing is just to low and to hard to handle with the 18" tires. I changed to a 14-38, which made a big improvement. I’m even considering going to a 37 or 36 tooth rear. Its different for each track, if your picky about changing gears allot.

 

I run 14/37 on my modded R now for MX racing. While I may loose some acceleration with the taller gears, I cut down on the shifting time for the straights.

But each track is different.