The chain connects the engine to the rear wheel, and it carries every horsepower the bike makes. A chain in poor condition wears out the sprockets, wastes power and can break. A little regular attention keeps it quiet and safe.
Checking tension
- Put the bike on its stand or a paddock stand so the rear wheel is off the ground, or on level ground with the bike upright, as the manual says.
- Turn the wheel and find the tightest point of the chain. Chains wear unevenly, so tension varies as the wheel turns.
- Measure the free play at the tightest point, at the middle of the lower run. The manual gives the figure, often between about 20 and 30 mm.
- Adjust with the rear axle, and keep the wheel in line. Use the marks on the swingarm and check the alignment by eye or with a straight edge.
A chain that is too tight wears the gearbox bearing and the sprockets. A chain that is too loose can jump off the sprockets.
Cleaning and lubricating
- Clean the chain with a brush and a suitable chain cleaner or paraffin. Do not use strong solvents on an O-ring or X-ring chain, since they can damage the seals.
- Dry it and apply chain lubricant to the inner side of the lower run, where it can travel to the rollers.
- Lubricate every few hundred kilometres and after rain. Wipe off excess so it does not fling onto the rear wheel.
- On bikes with an oil bath chain case, check the oil level and the case seals.
Wear and replacement
- Stiff links that do not move freely mean the chain is dry or corroded.
- If the chain can be pulled away from the rear sprocket so that you can see a gap or the teeth look hooked, it is worn.
- Check the length against the limit that the chain maker or the manual gives.
- Replace the chain and both sprockets together. A new chain on worn sprockets wears out quickly.
- Use the master link correctly. The clip is fitted with its closed end facing the direction of the chain's travel.
Shaft drive
Bikes with shaft drive, such as many BMWs and Moto Guzzis, have no chain but a final drive housing that needs its own care.
- Change the final drive oil at the interval in the manual, and use the grade specified.
- Check for leaks at the pinion seal and the rear wheel drive.
- Inspect the rubber boot on the shaft. Cracked boots let in water and dirt.
- Grease the splines at the interval in the manual. Dry splines wear and can cause a clunk when you open the throttle.
- Listen for whine or noise and feel for play. Play in the drive can mean worn parts.
Belt and other systems
Some bikes have belt drives on the primary or final drive, and some old British bikes have a chain in an oil-filled case. Follow the manual for each. Never run a belt that is cracked or has damaged teeth.
Safety
- Fit the chain guard if the bike has one.
- Never lubricate the chain with the engine running and the wheel turning, unless you know exactly what you are doing.
- Check the sprocket nuts and the lock plates when the chain is changed.
