Category:Cassette (Rear Wheel Gears)

I replaced my stock single speed gear with a Shimano 7-Speed Trouney Bicycle Freewheel Replacement Cluster - MF-TZ2. It wasn't all that expensive either (about $15 - $20 with shipping). The old gear comes off pretty easily. Just tap a hole punch or nail at an angle into one of the dimples on the surface of the old gear. It loosens easily. You just unscrew it and screw on the new one. Don't worry about getting it tight enough because you'll tighten it up evry time you pedal. You'll need a rear derailleur and a new longer chain, but a bike shop should be able to find the compatible parts for you.

I took off the electric parts and put them on my wife's old mountain bike. Here's what it looks like: