Originally Posted by Alex

Plenty of people have made various sprocket swaps. Here's the first DIY that pops up:

http://www.ninjette.org/forums/showthread.php?t=10273

The most common switch seems to be going slightly taller gearing, either changing the front sprocket to a 15-tooth (from stock 14), or lowering the rear from the stock 45-tooth to a 42 or a 43. Going in that direction lowers revs slightly for a given road speed, making the bike a little less "busy-feeling" on the highway. But it would lower effective torque at the same road speed.

Going in the other direction to make the gearing shorter is a bit rarer, though some have done it. This could help the feeling of torque pulling from a stop, but would cause the bike to be running higher revs while cruising. For what it's worth, one of the folks that went to a very tall ratio (15 front / 41 rear), found that gave him the best quarter mile acceleration,