The only thing that sucks is picking the right set up. My 250 is geared great for the woods, but when we hit the road, i am literally left in the dust.  What gearing do you have now. And you are just looking to get more top end right.
1 tooth on the front is 3 on the rear to the plus side. So going from 13-40 to 14-40 will give you more top end, it would be like 3 more teeth added to the rear.
 There is a gearing calculator on everything2stroke.com
Maybe that can help you out a bit more, but i guess you need to find out what how fast your buddies bikes are running at top end. But remember top speed is at max rpm. So I don't think you want to be pinging it wide open for a long time. Your gonna lose bottom end, but really who uses first gear anyhow. LoL