I have a 400ex frame with a 96 rm250 motor. My own 250r. I got it geared at 13/42 i can climb anything and walk all over stock 450s in the woods. But i top out at 50 cant keep up on the top end. Woods im waiting for people but once we open up on the logging roads im left behind. Far behind. What gear ratio should i go for was thinking 13/38 and going from 18 inch tire to 20 in rear.

 

If you ride anywhere other than the track, most definitely get rid of the 18" tires. You might even consider 22" over 20", depending on ground clearance needed. Find the tire size you like first, then if needed, work with you gearing. It sounds like an interesting machine. Post some pics.

 

22s? I dont ride trails thats for 2 wheels ha. How much does the tire change the speed? Feels like i should have 2 more gears.

 

If you are riding in the woods, are you not riding on the trails? I do not know how accurate this is, but I read that 2 inches on your rear tires is equal to about 1 tooth on your cs sprocket. A one tooth change on my cs sprocket made quite a bit of difference. My TRX700XX is geared high from the factory and does not like to be lugged around. This makes it easy to stall when lugging it around. I wanted just the opposite of what you want. I went 1 tooth smaller and love it. Naturally, it did affect my top end, but since I don't ride wide open most of the time, the trade off was worth it. If you are going to switch to a 20" tire anyway, do that first and see how you like it. If it is still WAY too slow on top, and you don't mind losing your low end grunt, try 2 teeth larger on the front, assuming there is room for it.

 

Technicly its trails but really its pipelines and abandond logging roads. Powerlines etc. Thanks for the reply. Looking at a pair of buckshot 22s used im gonna try and see what the diffrence is.

 

Got some buckshot 22s. They dont make tires like that no more. They hook amazing. Gave me alittle more topend to play with but i could use more.

 

Good. Now you can play with either you cs sprocket or your rear sprocket. If you are still way off on your top end, try going either 2 teeth larger on the cs or 1 to 2 teeth smaller on the rear. Post some pics. I would like to see your quad and the tires.