Well i have a 2004 400ex. I just ordered a 13 tooth front sprocket i was wondering what would go good with that for a back sprocket that wouldn't take that much top speed away?

 

I race hair scramnles and ride trails on a 00ex. I run a 13/39 setup. Try that setup and you may never look back. But if your riding wide open I'd run a 14 or 15 in front and a 40 rear. It won't be a torque monster tho.

 

I ran a 13/38 combo on my stock motor and would hit the rev limiter in 5th gear quite fast but trail riding was more enjoyable as tight low speed turns were easy to crawl through without feathering the clutch. I also run 22" rear tires. After the 500cc bbk I went back to a 15/38 combo and when these tires wear out Im going back to 20" rear

 

I have a sparks slip on open aluminum airbox uni filter 6 degree timing advance and no choke. I run the 13/39 for low end. I can keep up with a 450 till the woods. Then its my turn to get out front and kick aSpam wordSpam word Spam wordSpam word Spam wordSpam word Spam wordSpam word . I don't get 5th gear often tho