There are a number of different chain sizes. The most popular for scooter and electric bikes are no. 25 and no.35. Small sprockets come with a D-shaft or a shaft with set screws. For set screws, drill a small hole in the motor shaft for permanent mounting, then secure with green or blue loctite. For a d-shaft hole, you must secure the sprocket with a nut and washer, otherwise it will just slide off the motor shaft.
No. 25 chain
Cost per foot: about $8 or $9
Cost of a small sprocket: $12-$20
Cost of a large sprocket: $20-$35
Small sprockets range from 11 to 25 teeth and have shaft sizes of 8mm, 1/2″, 3/8″.
This chain is really ‘compact.’ It isn’t as strong as #35 but heavy duty #25 will do for relatively low powered scooters and bikes. I’m not too crazy about this chain. I abused my chain during testing and it ended up being less than straight.
No. 35 chain
Cost per foot: about $2
Cost of a small sprocket: $8 (McMaster)
Cost of a large sprocket: $18 (McMaster)
Popular on go karts. The sprockets cost about the same (with comparable number of teeth, you can purchase sprockets with far more teeth than No.25), though the chain costs a lot less. I’d go with this chain for the next project.
Single Speed Bicycle Chain
This is wider than chain for multispeed bikes. 1/2″x1/8″
Derailleur Bicycle Chain
3/32″ wide
Here are some pictures of the No.25 chain on this electric bicycle.
This is the more common type of rear wheel, where the gear set screws on. BMX style wheels have a cassette instead (search Youtube for instructions).
The No.25 80 tooth sprocket mounted on a 20″ rear wheel (on the front of the bike)
Same wheel as the previous picture, but viewed from the other side
A no.25 masterlink