This guide shows you how to easily remove & replace the drive sprocket on a motorized bicycle engine.
1. Remove the pin from the center of the drive sprocket to start with. You can also remove the ball from behind the pin.
2. Take an extra chain link and jam it in between the sprocket and the engine case (shown in the picture above).
3. Use the correct socket spanner to remove the bolt. It takes some force to loosen the nut. Remove the bolt and the jagged washer.
Drive Sprocket Removal Tool
4. Spin the drive sprocket removal tool (shown below), all the way into the center of the sprocket.
5. Use a shifting spanner and spin the center part of the sprocket removal tool clockwise into the sprocket until the sprocket loosens and comes away from the shaft.
6. Put your hand underneath the sprocket to catch the very small half moon key that locks the sprocket in place.
Installing a New Sprocket
7. Put on a new sprocket and place the locking key back into the correct position. Tap the sprocket with a mallet until it sits in its place.
8. Replace the washer and tighten the nut using the spare piece of chain to once again lock the sprocket into position.