Chain, belt and shaft final drive
Chain, belt and shaft final drive are three ways of turning the rear wheel, with three completely different maintenance routines.
Final drive
Three ways of getting power from the gearbox to the wheel are in common use, and they demand completely different amounts of an owner's attention. A roller chain is light, efficient and adjustable, and it wants cleaning, lubricating and tension checking at intervals measured in hundreds of miles, then replacing as a set with both sprockets.
A toothed belt asks for almost nothing between inspections and fails rarely but without much warning. A shaft asks for a lubricant change at a long interval and is otherwise invisible.
A chain designation specifies pitch and width. Installation also requires the correct length, sprocket tooth form, offset and model fitment; matching 520 or 525 alone does not establish compatibility.
Reading a chain size
A chain designation such as 520 carries two facts. The first digit gives the pitch, the distance between pin centers, in eighths of an inch. So a 5 means five-eighths of an inch.
520, 525 and 530 share 5/8-inch pitch but require their matching sprocket tooth widths. D.I.D.’s dimensional chart distinguishes inner width as well as pitch. The matching pitch alone does not make sprockets interchangeable.
| Designation | Pitch | Where it is usually found |
|---|---|---|
| 420 | 1/2 in | Small-displacement machines, pit bikes, youth models. |
| 428 | 1/2 in | Wider roller than 420. Small road and trail bikes; not interchangeable with 420 sprockets. |
| 520 | 5/8 in | The lightest of the 5/8 in family. Common on sport bikes and as a conversion size. |
| 525 | 5/8 in | Wider than 520, stronger, slightly heavier. Very common original fitment. |
| 530 | 5/8 in | The widest of the three. Larger touring and older large-displacement machines. |
Pitch and width are dimensional standards, so a designation means the same thing from any manufacturer. What varies by brand is the sealing type, the plate material and the tensile rating. Those, unlike the size, are worth paying for.
O-ring, X-ring and plain chain
A plain chain has no seal at the pin. So its internal lubrication depends entirely on what you apply and how much of it survives the last rain. A sealed chain traps factory grease inside each joint behind a rubber seal, and the lubricant you apply afterwards is mostly for the rollers and the external surfaces instead of for the pins.
The seal profile is the difference between the two sealed types: the X-shaped profile deforms with less friction than a round O-ring for the same sealing performance. Both outlast a plain chain considerably in wet or dirty conditions, and both are ruined by a solvent that attacks the seals, which is why chain cleaner choice matters more on a sealed chain than on a plain one.
How a chain wears out
Chains do not stretch as longer metal. Material is worn away from the pins and the inside of the bushes, so each joint gains a fraction of play, and across a hundred-odd joints those fractions add up to a chain that measures longer than it did. That is why the wear check is a length measurement over a stated number of links, not a look at the rollers.
A worn chain also stops matching its sprockets. The pitch it has grown to no longer aligns with the tooth spacing, so the load concentrates on fewer teeth and the sprockets wear into a hooked profile. This is why chains and sprockets are replaced as a set: a new chain on hooked sprockets is destroyed quickly.
A new sprocket on a worn chain gets hooked.
Tension, and the mistake almost everyone makes
A chain must be slack at the point where the run between the sprockets is at its tightest. That point is not the same all the way round the wheel. A chain with uneven wear has tight spots.
Rotating the wheel and finding the tightest point, then setting the slack there, is what stops a chain being over-tightened at one part of its rotation. Set at a random point, it can run tight.
The other half of the mistake is measuring at the wrong suspension position. Chain tension changes as the suspension moves, because the swingarm pivot and the countershaft are not concentric. Manuals specify the condition to measure in, usually unladen and on the sidestand or a stand, and a chain set correctly under one condition can be far too tight under another.
The slack range in millimeters, the wear service limit over a stated number of links. The axle nut torque are all model-specific. Set them from your own manual.
For a sprocket change, the gearing calculator compares ratios and fixed-ratio road speed or rpm. Physical chain length needs the installation dimensions and adjuster range; the calculator does not size it. Gearing calculator
Belt and shaft, briefly
A belt final drive uses a toothed belt running on toothed pulleys, and it is essentially a sealed system from an owner's point of view: inspect it for cracking, missing teeth and debris, check the tension if the manual gives a method. Otherwise leave it alone.
Inspect a drive belt using the manual’s wear, damage and adjustment procedure. Visible wear and contamination need attention before a belt breaks.
A shaft drive runs a bevel gearset in oil. The maintenance is a lubricant change at a long interval, using the gear oil category the manual specifies. That category matters, because the more aggressive extreme-pressure additive package can attack copper-alloy components in some gearsets.
Beyond that, a shaft asks nothing until a seal or a bearing goes.
References
- Standard API Engine Oil Licensing and Certification System: service categories: American Petroleum Institute.
Final drive
Three ways of getting power from the gearbox to the wheel are in common use, and they demand completely different amounts of an owner's attention. A roller chain is light, efficient and adjustable, and it wants cleaning, lubricating and tension checking at intervals measured in hundreds of miles, then replacing as a set with both sprockets. A toothed belt asks for almost nothing between inspections and fails rarely but without much warning.
A shaft asks for a lubricant change at a long interval and is otherwise invisible. Chain sizes are a published designation, the 520 and 525 you see quoted are standard pitch and width codes, not brand names, which is why chain fitment is one of the few powersports questions with a universal answer. Slack, wear limit and torque are model-specific.
Reading a chain size
A chain designation such as 520 carries two facts. The first digit gives the pitch, the distance between pin centers, in eighths of an inch. So a 5 means five-eighths of an inch. The remaining digits encode the roller width.
That is why 520, 525 and 530 chains all share the same pitch and the same sprockets, and differ in how wide the rollers and side plates are, and why a 428 chain is a different pitch that needs different sprockets.
Chain, belt and shaft drive questions
What does 520 mean on a motorcycle chain?
The first digit encodes the pitch in eighths of an inch, so 5 means a five-eighths inch pitch measured between pin centers. The remaining digits encode roller width. A 520, 525 and 530 chain therefore all share pitch and sprockets and differ in width and strength, while a 428 chain has a different pitch and needs different sprockets entirely.
Can I fit a 520 chain in place of a 525?
Only with matching 520 sprockets, because the sprocket tooth thickness differs even though the pitch is the same. It is a common conversion, done to save rotating weight, and it is a set change instead of a chain change. The trade is a slightly lower tensile rating for less unsprung and rotating mass.
What is the difference between an O ring and an X ring chain?
The seal shape that traps grease inside each joint. An X-shaped profile makes contact at fewer points than a round O-ring, so it seals as well with less drag. Both keep factory lubricant in and contamination out, and both substantially outlast an unsealed chain in wet or dirty conditions.
Does chain lube do anything on a sealed chain?
Yes, but a different job than most people assume. The pins and bushes are already lubricated behind the seals and nothing you apply reaches them. What you are lubricating is the rollers against the sprocket teeth, and protecting the outer surfaces and the seals themselves from corrosion and drying out.
Why do chains and sprockets have to be replaced together?
Because a worn chain no longer matches the tooth spacing it runs on, so it wears the sprockets into a hooked profile. A new chain dropped onto hooked sprockets is destroyed quickly by the mismatch. A new sprocket paired with a worn chain simply gets hooked in turn. Replacing all three together is cheaper than twice.
How do I measure chain wear?
By length over a stated number of links, with the chain under a specified tension, compared against the service limit in your manual. Chains do not stretch: material is worn from pins and bushes so each joint gains play, and the accumulated play across the whole chain measures as extra length. Looking at the rollers tells you almost nothing.
Where do I check chain slack?
At the tightest point in the chain’s rotation, found by turning the wheel and watching the free play change. Uneven wear produces tight spots, and setting slack at a loose spot leaves the chain bar-tight when the tight spot comes round. Measure in the suspension condition the manual specifies, because tension changes as the swingarm moves.
What happens if a chain is too tight?
It loads the countershaft and wheel bearings continuously, and at full suspension compression it can be tight enough to damage the gearbox output seal or bearing. A tight chain destroys more than a loose one. It is the more common error because a slack chain looks wrong and a tight chain looks tidy.
Can I clean a sealed chain with degreaser?
Only with a product stated safe for seals. Aggressive solvents attack the rubber seals, and once those are damaged the factory grease escapes and contamination enters, which is the failure the sealed design exists to prevent. Kerosene or a purpose-made chain cleaner with a soft brush is the conventional approach.
Is belt drive lower maintenance than chain?
Considerably, in routine terms. A belt needs inspecting for cracks, missing teeth, debris. A tension check where the manual gives a method, and very little else. The trade is that a belt failure tends to be sudden and complete, not progressive, and belts and their pulleys are more expensive when the time comes.
What maintenance does a shaft drive need?
A gear oil change at the interval in the manual, using the API gear lubricant category specified. That category matters: the more aggressive extreme-pressure package can attack copper-alloy components in some gearsets. So the specification is not a suggestion. Otherwise a shaft needs nothing until a seal fails.
How long should a chain last?
Anywhere from a few thousand miles to well over twenty thousand, depending on chain type, how often it is lubricated, conditions and power. A sealed chain kept clean and adjusted on a road bike lasts several times as long as an unsealed one on a machine ridden in mud. Because the range is that wide, the wear measurement is the answer and not any mileage figure.
Where the figures and rules come from
- Standard
- Short-pitch transmission precision roller and bush chains, attachments and associated chain sprockets : International Organization for Standardization, ISO 606; Standard; API Engine Oil Licensing and Certification System: service categories : American Petroleum Institute.
Final drive gearing: what a sprocket change does; Ratio change, engine speed at a given road speed, and the chain length implication.
- Sprocket fitment: pitch, width, splines and chain line
- The four things a sprocket has to match, and how each mismatch shows up.
- Motorcycle oil and the gear oil categories
- Which API gear lubricant category a shaft drive wants.
- Service intervals for chain and belt inspection
- Chain lubrication follows rain and washing, not any counter.