(1) Chain manufacturers want to build strong yet light chains. To get
strength, they can increase the roller diameter and pin diameter, but
this increases weight as well. They look for better materials and
manufacturing processes so they can decrease the amount of material and
weight accordingly. Chains must have great tensile strength, withstand
large impacts and handle the incredibly abrasive environment of a
(2) There are several distinct chain components. Side plates: these are
the actual linking portions of the chain. There are inner and outer side
plates, and each has a different design. O-ring chains: in a sealed
chain or O-ring chain, the inner and outer side plates are separated by a
type of rubber seal. Rollers: in the center of the chain are rollers,
which are the contact area for the sprockets. Pins: the axis of the
rollers are the pins. Usually, bushings separate the rollers from the
pins, but there are bushing-less designs.
(3) The size of a chain is designated by a three-digit number (520, for
example). The distance from the center of one pin to the center of the
next is called pitch. Pitch is represented by the first digit, which is
4, 5 or 6. Although some companies have converted their numbers to
decimals, the majority of measurements are in eighths of an inch. A 4
means 4/8-inch; a 5 means 5/8-inch; a 6 means 6/8-inch. The meaning of
the second number can vary. Most commonly, it designates the width of a
chain (from the inside of one inner side plate to the other). Adding to
the complication is roller diameter, which affects proper chain fitment
too. Width and roller diameter are associated with strength, so some
chains are given digits to represent their model and not necessarily
their size. The number may or may not reflect rated tensile strength.
(4) The master link is an important part of the chain, because without
proper attention, it can easily become the weak link. There are three
major types of connecting links. Slip-fit links are the most common type
on dirt bike chains. They have a clip that secures one side plate.
Second, press-fit links have a clip, too, but require a chain press or
“chain breaker” tool to install. Third, rivet links do not have clips;
they have hollow-ended pins that act like rivets and are flared out with
a tool to hold the side plate. Rivet links are better than press-fit
links, and press-fit links are better than slip-fit links. Press-fit and
rivet links are more common on street bike chain applications.
(5) You can install the clip on a slip-fit master link with a pair of
needle-nose or regular pliers. The clip can be leveraged off with a
flat-blade screwdriver. Be sure to avoid side loads that can bend the
thin clip during installation. Always be sure to use the supplied master
link that is provided with the chain. The pin diameter must match the
inner diameter of the roller it mates with.
(6) O-ring chains aren’t popular in the motocross world, but most
offroad riders swear by them. The seal sits between the inner and outer
side plates, and it keeps lube in and contaminants out from between the
pin and bushing. An actual O-ring is old technology. Now, O-ring chains
come with seals that have multiple lips (usually two or three) to
increase the number of contact points for better sealing. Sealed chains
and the sprockets with them last longer. They have the stigma of more
drag, but at operating temperature, many believe that sealed-ring chains
perform almost as well as non-sealed chains. Sizing is important, but
replacing an OEM O-ring chain with another O-ring chain isn’t mandatory,
as the manual may suggest.
(7) Chains elongate due to wear. Knowing when to replace a chain is a
judgment call for the average rider. It’s best to monitor the sprocket
teeth and grooves and replace all three components simultaneously. Fresh
drivetrain components have significantly different dimensions from
worn-out ones. When they don't mate properly, they wear their companion
parts very quickly.
(8) Improper chain adjustment will cause excessive wear. Ideally, the
chain will have just a bit of tension at its tightest point—when the
countershaft, swingarm and rear axle are aligned. Three fingers is the
rule of thumb, but be aware of what that slack is supposed to achieve.
Getting the sprocket perfectly in line with the chain is crucial. It’s
best to double-check the axle marks by measuring to the swingarm pivot
and watching the chain engage the sprocket. There are also special
visual alignment aids on the market.
(9) Proper cleaning and lubrication can drastically increase a chain’s
lifespan and make the rear wheel spin noticeably freer. Avoid direct
pressure from washer sprays and wire brushes, especially with an O-ring
chain. They can force in contaminants and destroy seals. Use soap with a
degreaser to scrub and rinse manually. Avoid direct blasts of
compressed air for the same reasons as pressurized water. Dry with a
rag, then use a water dispersant/lube to prevent rust. Even though the
rollers only move slightly during operation, it’s crucial that they move
freely to prevent friction, especially as lubrication wears away.
(10) Lubricant should be applied to the pivot points on both sides of
the chain after each moto. Ideally, there should be a touch of lubricant
on the roller when it contacts the sprocket too. Lubricants attract
dirt, which is counterproductive. Focus on spraying an even—but not
excessive—coat on the top side of the chain as it passes underneath the
swingarm so that it sinks and wicks into the joints as the chain spins.
WD40 is great after washing, but use a chain-specific lube at the track.