Harley-Davidson Final-Drive Chains: Conversions, Gearing and Care

The short answer: Choose a chain conversion for a clear reason and have the complete arrangement specified for your motorcycle. Chain size, sprockets, alignment, clearance and gearing must work together. A chain also brings a maintenance routine that needs to suit how you use the bike.

Some Harley-Davidson motorcycles already use a final-drive chain. Others have been converted from their original belt arrangement.

For an owner considering a conversion, the starting question is straightforward: what do you want to achieve?

A change of appearance, a particular gearing requirement and a modified drivetrain are different reasons for considering the job. Each deserves a complete plan before parts are ordered.

Final-drive chain or primary chain?

The final drive transfers drive from the gearbox to the rear wheel.

On a chain-driven arrangement, a front sprocket drives a chain that turns the rear-wheel sprocket.

This is separate from the primary drive between the engine and clutch. A motorcycle can have a primary chain and a final-drive belt, so “my Harley has a chain” does not identify which system needs attention.

When asking about parts, specify whether you mean the rear-wheel final drive or the primary drive.

Our primary-chain guide covers the latter.

Decide what the conversion needs to achieve

Before comparing kits, write down the purpose of the change.

Are you trying to achieve a particular final-drive ratio? Accommodate a documented wheel or drivetrain modification? Complete a custom build?

If the existing belt arrangement is suitable and serviceable, consider what the conversion would improve for your riding.

Also think about ownership afterwards. A rider who enjoys regular maintenance may view chain care differently from someone who wants minimal routine attention between services.

Do not choose from the appearance of a rear sprocket alone. Compare the complete installation, maintenance requirements and intended result.

Specify the complete conversion

Use a documented conversion intended for the exact motorcycle and the equipment actually fitted.

Before ordering, establish:

• The motorcycle’s model and model year.
• The gearbox output and front-sprocket fitment.
• The rear wheel, hub and sprocket mounting arrangement.
• The specified chain size, type and required length.
• Front and rear sprocket tooth counts.
• Required offsets, spacers and retaining components.
• Chain-line and clearance requirements.
• The adjustment range and applicable fitting instructions.

Aftermarket wheels, wider tyres and suspension changes need to be included in the discussion.

Two components described as using the same chain size are not necessarily suitable together on your motorcycle. Their mounting, offset, strength and application still need confirming.

Ask the kit manufacturer and installer to explain the complete arrangement, including any implications for other fitted systems.

Understand the gearing arithmetic

For a simple final-drive chain arrangement:

Final-drive ratio = rear sprocket teeth ÷ front sprocket teeth

Consider these illustrative examples:

With the same gearbox ratio and tyre rolling circumference, the second combination produces approximately 4.2% more engine revolutions at a given road speed.

These figures explain the arithmetic. They are not recommended sprocket combinations for a particular Harley-Davidson.

In general, increasing the numerical final-drive ratio gives shorter gearing. Reducing it gives taller gearing.

Neither is automatically better. Ask how the proposed ratio compares with the current arrangement and how it suits your normal riding.

A change intended to make cruising more relaxed also needs to be assessed for its effect on pulling away and everyday operation. Choosing by tooth count alone leaves out the rest of the motorcycle.

Get alignment and clearance right

The chain needs to run in the intended line between the sprockets.

Do not assume that a sprocket bolting onto the wheel establishes correct alignment. The front sprocket, rear sprocket, wheel position and any specified offsets form one arrangement.

Clearance must also be assessed through the relevant suspension movement, using the conversion manufacturer’s procedure.

Ask the installer to confirm clearance around the tyre, swingarm, guards and nearby components. If the motorcycle has been lowered or fitted with different-length shocks, mention that before the installation is specified.

Keep the conversion instructions and component numbers with the motorcycle’s records. Future wheel or suspension work should take the modified final drive into account.

Adjust to the correct procedure

There is no universal chain-slack figure suitable for every converted Harley-Davidson.

Use the instructions for the motorcycle and conversion actually fitted, including the specified measuring position and loading condition.

Do not borrow a measurement from another model or tighten the chain until it merely looks neat.

The Great Britain motorcycle MOT manual identifies both excessively loose and excessively tight final drives as defects. Excessive tightness is not a safeguard against a chain coming off. [1]

After adjustment, complete the specified alignment, axle-tightening and final checks. If the adjustment varies noticeably as the wheel is turned, investigate the cause rather than choosing an average position and ignoring it.

Match the joining link to the chain

Use the joining link specified for the exact chain series and follow its manufacturer’s installation method.

Do not assume a link is suitable simply because the nominal chain size matches.

The required tools, assembly measurements and checks depend on the product. D.I.D, for example, publishes chain-specific riveting information and tool guidance. [2]

Joining a chain is a job where correct identification matters before force is applied. If the required equipment or instructions are unavailable, have the work completed by someone suitably equipped.

Accept the maintenance routine

Sealed chains still require external maintenance. Their seals do not remove the need for inspection, cleaning and lubrication.

Follow the chain manufacturer’s intervals and account for wet, dirty or salty conditions. RK specifically notes that adverse conditions can shorten chain life and require additional maintenance. [3]

Choose products approved for the chain’s sealing system. D.I.D recommends O-ring/X-ring-safe cleaners and lubricants and advises against kerosene for its drive chains. [4]

Do not assume a cleaner suitable for another workshop task is suitable for chain seals.

Keep the engine stopped during chain maintenance. Never use engine power to turn the rear wheel while cleaning or lubricating the chain.

Keep fingers, cloths and tools away from the chain and sprocket engagement points.

Inspect the chain and sprockets together

Pay attention to stiff links, corrosion, damaged seals, cracked plates and changing adjustment behaviour.

RK identifies these as warning signs requiring attention, with cracked links and damaged seals among the conditions calling for immediate replacement. It also recommends replacing front and rear sprockets alongside the chain. [3]

Follow the applicable manufacturer’s inspection and replacement criteria rather than waiting for the adjustment to run out.

If wear develops unusually quickly, ask why. Alignment, adjustment, component compatibility and maintenance should be checked before simply fitting another chain.

Prepare a useful parts enquiry

For an existing conversion, provide more than the motorcycle’s original model details.

Include:

• The conversion-kit manufacturer and part number.
• Front and rear sprocket tooth counts.
• Chain manufacturer, series and size.
• Rear-wheel details and relevant modifications.
• Photographs of the fitted arrangement.
• The problem you are trying to solve.

For a proposed conversion, explain how you use the motorcycle and what result you want.

A useful question is:

“What complete combination is specified for this bike, and what fitting and maintenance information comes with it?”

That is a stronger starting point than ordering a chain and two sprockets independently.

The Hogparts view

Choose a chain conversion around a defined purpose and a properly specified installation.

For a road motorcycle, correct fitment, suitable gearing and a maintenance routine you will follow matter more than appearance alone.

Once the arrangement is established, keep its details. Good records make future servicing and replacement-part enquiries considerably easier.

Sources and further reading

1. DVSA: Motorcycle MOT inspection manual, structure and attachments, transmission section
2. D.I.D: Chain maintenance and installation information
3. RK: Chain maintenance and warning signs
4. D.I.D: Frequently asked questions and chain-care guidance

Always follow the motorcycle, conversion-kit and chain manufacturers’ instructions. Conversion work and safety-critical maintenance should be completed by a suitably equipped, competent motorcycle technician.

Related guides

• Harley-Davidson Drive Belts Explained
• Harley-Davidson Primary Chains Explained
• How to Check Harley-Davidson Part Fitment Before You Buy

About Hogparts

Hogparts UK Ltd is an independent retailer of aftermarket motorcycle parts. We are not affiliated with, authorised by or endorsed by Harley-Davidson.