I changed my rear sprocket from a stock 40 to a 48 tooth, it made an amazing difference. I primarily use the bike for off road, but it didn't really hurt my on road speed much. It's possible to start off in 2nd gear with very little slipping of the clutch. Front tire comes off the ground very easy now. I'm still working on modifying the rear chain guide, but it looks very simple. I wish I would've done this a long time ago.