Chains are not only cheap and reliable, they?re the most efficient form of final drive for a motorcycle. When you boil it down, chains come in two varieties: standard (or unsealed), and O-ring (or sealed). Photos by the author.

Take a look around any dealership floor, bike night parking lot or race paddock, and the vast majority of motorcycles will be wearing a chain and sprockets for their final drive. Belts and driveshafts have their perks, but chains are the dominant drivetrain thanks to their low production cost, efficient power transmission and easy gearing changes and component replacement.

Chains basically come in two categories: unsealed or standard roller chain, and sealed or O-ring chain. Unsealed chains are commonly found on vintage bikes, small-displacement economy rides and off-road motorcycles. They?re what you see on bicycles and conveyor belts, and even the treads on a bulldozer are a type of unsealed chain. Standard chain is just a series of plain bearings made of metal links and nothing else. That means it?s up to you to apply lubricant to keep the parts from grinding themselves into dust, and you have to do it every few hundred miles. Even then, reducing friction between high-wear components like the link pins and bushings is difficult, and as a result unsealed chains wear quickly, necessitating frequent slack adjustments and replacement.
Sealed chains, as the name suggests, have rubber seals sandwiched between the side plates and inner links, se...