What size chain / sprocket do I need?

It depends entirely on the number of teeth on your existing sprockets and the number of links in your existing chain. Start with counting all of that. This video may help. 

If you're keeping your gear ratio the same, simply order replacements that match the tooth/link count on your current parts. If you're changing your gear ratio there are a few things to consider. 

As each link alternates between an inner and outer link, any variation in chain length will be a multiple of two. 

A larger sprocket (either front or rear) with the same length of chain will pull the wheel forward in the axle dropout. The opposite applies for a smaller sprocket. Depending on where your wheel sits in the slot, you may be able to go up or down in sprocket size without changing your chain length.

Chain length and wheel position varies bike to bike. Good news is you can return the unused chain if you end up needing a different size. You can error on the longer side and cut the chain down if need be. We carry chain breakers if you don't have one already.

There are a few known factory sizes that might help: 

Factory Chain Lengths Based on Factory Sprocket Tooth Count

• CB350 - 16 F / 36 R = 94 link
• CL350 - 16 F / 38 R = 96 link
• CB360 - 16 F / 34 R = 94 link
• CL360 - 16 F / 34 R = 94 link
• CJ360 - 16 F / 33 R = 98 link
• CB450 - 15 F / 35 R = 92 link
• CL450 - 15 F / 35 R = 92 link
• CB500T - 15 F / 33 R = 96 link
• CB550K - 17 F / 37 R = 100 link
• CB550F - 17 F / 37 R = 100 link