Roller chains are typically found in situations that require maximum power transfer, in a small space, at an economical price. ATVs, motorcycles and scooters often use a drive chain, drive sprocket and driven sprocket to transfer power from engine to the wheel(s).

Because of the demands put on a motorcycle drive chain it is important to constantly inspect and maintain the chain so that it remains serviceable. A chain’s condition can be determined by grasping one link that’s in contact with the rear sprocket and pulling it up – if the link comes more than halfway off a sprocket tooth, the chain should be removed and measured. Measure the chain from pin to pin and compare to the service limit (often printed in your vehicle’s corresponding service manual).

As a chain wears so too do the sprockets on which it rides. Sprocket wear is usually indicated by the hooking or breaking off of sprocket teeth. Chains and sprockets should always be replaced as a set.

Chains are available in a variety of patented designs, however, they fall into two main groups; sealed and non-sealed. O-rings are often used to seal lubrication inside of a sealed chain – the o-rings also keep dirt and moisture out of the chain internals.

Roller chains form an endless loop and are usually connected by either a removable master link or permanent rivet.

The anatomy of a chain consists of alternating inner and outer links. An inner link is made of two plates held together by two press fit bushings upon which two rollers ride. An outer link is made of two plates held together by two press fit pins passing through the bushings of the inner links.

The following illustration depicts how to properly measure a chain to determine its size.

Roller chains are available in a variety of common sizes – often the chain size is stamped directly on side of the the chain. The following table lists common chain sizes, crossover and specifications.

A castle nut, or castellated nut is a specialized nut that is sometimes used on motorcycle axles, swingarms or any application where it is crucial that the nut not be permitted to vibrate off.

Generally the end of the bolt where the castellated nut threads on will have a hole drilled through it. Since the nut is notched it allows a mechanic to tighten up a bolt and align one of the notches in the nut with the hole in the bolt. This way a cotter pin can be inserted through the nut and bolt and bent over. The cotter pin prevents the fastener from coming apart.