Re: What do you think? Shift kit or new sprocket?
I own both... and commute 32 miles each day, round trip. I have a 32 tooth rear sprocket (from BGF, $19.95); top speed is 38mph on both with Jet Stealth 80cc engines. The shift kit, in stop and go traffic, is the best. It's a little more "fiddlely" (more complex, more adjustments), but I can do the whole commute with out peddling. The small 32 tooth sprocket requires peddling to start and anytime I slow below 8-10 mph, but only for a bit. I have found myself gravitating to "sprocket bike" because of the simplicity. On the weekends, I ride the shifter bike. I have not played with the 8-speed ratio's on the shifter bike yet, to optimize the ride. In low gear, the bike speed is under 8mph @ wot... I do not have a need for that much torque (not too many hills in the panhandle of Florida).
Sooo... bang for the buck: low tooth count sprocket. Added bonus, simple setup, less to worry about. But for "performance riding, hill climbing, or just out right FUN!": shifter kit!