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.

The Constant-Velocity Joint allows a rotating shaft to transmit power through a variable angle, at constant rotational speed, without any significant increases in friction or play. CV Joints are commonly used at ends of the axle halfshafts on four wheel drive ATVs.

These joints are very strong and low maintenance. The most common maintenance item is to check the condition of the  rubber gaiter (dust/weather boot) that covers the joint is secure and not split. If the gaiter is damaged, the molybdenum disulfide grease with which the joint is packed will be thrown out. The joint will then pick up dirt, water, and small rocks and cause the joint to overheat and wear. The grease can also contaminate the brakes. In worst case, the CV joint may disjoin causing the vehicle to stop moving or lock up, rendering the ATV incapable of steering.

A motorcycle clutch basket is a bowl-shaped gear-driven housing bolted onto the end of the clutch shaft. Its job is to hold the entire clutch assembly together. When servicing your clutch it is important to inspect your clutch basket for cracks and wear. Your service manual will generally provide service specifications for your motorcycle.

Clutch springs can be found in use on most motorcycle clutch assemblies. The function of these short coil springs is to continuously hold the friction and driven plates together through spring tension, preventing slippage except when the clutch lever is engaged. Most often, five or more clutch springs are used per motorcycle clutch assembly. Stiffer or more springs are typical of higher output engines. Softer or fewer springs beget a lighter clutch lever pulling effort. When servicing your clutch it is important to check the free length of your clutch springs. If they are out of specification they can cause your clutch to slip which will result in premature failure of other clutch components, loss of power and mileage.

Customized motorcycle built in the style currently categorized as a sportbike; popular in the 1960s, 1970s and early 1980s. The term originated in England when it was popular to modify a motorcycle for better performance and riders would race from cafe to cafe. Sometimes a jukebox would be started to play a particular song at a cafe and riders would race around a prescribed route to see if they could make it back to the cafe before the song was over.

The mixing of air with a fluid. When air is allowed to enter the oil pump of a motorcycle engine it can cause a situation where the oil is displaced and unable to flow properly through the pump. A solution is often to bleed the air out of the lubrication system. Cavitation can also be a problem with personal watercraft when air mixes with the water in the pump drive system.

Refers to the diameter of the cylinder that the piston fits into in a motorcycle engine.

A precisely machined hole in the cylinder block of a motorcycle engine. The cylinder guides the piston as it travels up and down inside it.

A chain running between the crankshaft and camshaft on overhead camshaft four stroke engines. This is often called a timing chain because it “times” the crankshaft to the camshaft so that the valves open and close at the proper time. Motorcycle cam chains can be a roller type (similar to the chain driving the rear wheel but much smaller) or a Hy Vo multi plate type. Other methods of connecting the crankshaft and camshaft are gear drive, shaft drive and toothed rubber belt drive.