For the left side, there should be a nut and threaded stud on the crank near the rotating point. Loosen the nut so that it's just about off the stud (maybe a little past being flush with the end of the stud). Take a hammer and tap on it a little bit until it loosens the stud and pushes it out a bit. Then take the nut off and the stud should pull out the rest of the way. The crank should slide off, then. On most maxi's, they have a two-piece crank, and the right crank is permanently attached to the sproket and shaft assy. but the left one comes off, so if you want to replace both cranks, you'll probably have to replace the shaft and sproket, too. If your bike is an MKII or on some other bikes, the crank is three pieces instead of two.