How much faster from the stock 13 front and 38 rear will changing the front to a 14, or rear to a 39 make one and how much power do you lose?

 

Putting a 14 on front will give you maybe 3/5 mph. That's a guess. Going up on the rear will slow you down, to gain speed with a rear sprocket change you need to go down to a 36. A gearing change, in my opinion, is a must on a 300EX, especially with 20" tires.

 

ok which is better going up on front or down on rear? what do they work for low/mid/ot top|?