How to Check and Adjust Motorcycle Chain Tension

Push up on the bottom run of your chain halfway between the sprockets. If it moves more than about 40 millimetres, or less than 20, something needs doing. That simple test takes ten seconds, and it is the one most riders skip until they hear a slap on a downshift or feel the drive snatch at low speed.

Motorcycle chain tension and lubrication decide how long a chain and sprocket set lasts, and a new set fitted at a workshop typically costs a few hundred pounds once labour is included. Done properly, a decent O ring chain can last well beyond 15,000 miles. Neglected, the same chain can be finished in a third of that. Here is how I check, adjust and lube a chain at home with basic tools.

What Correct Motorcycle Chain Tension Looks Like

There is no universal number, which is why the first step is always the owner's manual or the sticker on the swingarm. Most road bikes sit somewhere between 25 and 35 millimetres of total free play, roughly 1 to 1.4 inches. Adventure and off road bikes with long travel suspension often need more, sometimes 40 to 50 millimetres.

Bike type	Typical slack range	Why
Sports and naked road bikes	25 to 35 mm	Shorter suspension travel
Commuters and small capacity bikes	20 to 30 mm	Light chains, short swingarms
Adventure and dual sport	35 to 50 mm	Long travel changes chain path a lot

Also note how the manual wants the bike positioned: on the side stand, on a centre stand, or with a rider aboard. Each gives a different reading.

How to Measure Slack Properly

Put the bike in neutral and position it as the manual specifies.
Find the midpoint of the lower chain run between the two sprockets.
Push the chain up with a finger and hold a ruler against it to note the top point, then pull down and note the bottom. The difference is your free play.
Roll the bike forward a quarter turn of the rear wheel and measure again. Repeat all the way round.
Use the tightest reading as your measurement.

Chains stretch unevenly. If your readings differ by more than about 10 millimetres around the wheel, the chain has tight spots, which usually means it is near the end of its life.

Why Tighter Is Not Safer

A lot of riders, and some well meaning friends with spanners, tighten a chain until it barely moves because a loose chain sounds dangerous. A tight chain is worse.

As the rear suspension compresses, the distance between the gearbox sprocket and the rear axle changes, and on most bikes the chain gets tighter through part of that travel. A chain set with too little slack at rest can go bar tight over a bump. That loads the gearbox output shaft bearing, wears the sprockets quickly and can make the rear suspension feel harsh.

So when you are unsure, err on the looser end of the manufacturer's range, not below it. Slightly loose is a maintenance item. Too tight can mean a gearbox repair.

Adjusting the Chain Step by Step

You will usually need a socket for the rear axle nut, two spanners for the adjusters and, ideally, a torque wrench.

Loosen the rear axle nut just enough that the wheel can slide. Do not remove it.
Turn each adjuster by the same amount, a quarter turn at a time, counting as you go.
Check the alignment marks on both sides of the swingarm match.
Recheck slack at the tightest spot.
Push the wheel forward against the adjusters, then tighten the axle nut to the specified torque.
Lock any adjuster lock nuts and check slack one final time, because tightening the axle can shift it slightly.

Swingarm marks are not always accurate. Sight along the chain from behind the rear sprocket; it should run straight onto the teeth without bending sideways.

Cleaning and Lubricating Without Overdoing It

How Often

For most road riding, lube every 300 to 500 miles and after any ride in rain or on salted roads. Riding daily through a wet winter, once a week is sensible. Many riders lube before every ride, which mostly flings oil onto the wheel and collects grit that acts like grinding paste.

How to Apply It

Lube after a ride when the chain is warm, so it penetrates better.
Spray onto the inside of the lower run, aiming at the rollers and where the side plates meet.
Rotate the wheel slowly by hand, never with the engine running in gear.
Leave it to set for at least an hour, ideally overnight, then wipe off the excess.

Cleaning

Every 1,000 miles or so, clean the chain with a dedicated chain cleaner or paraffin and a soft brush. Avoid pressure washers aimed directly at the chain, and harsh solvents, both of which can damage the O ring seals that keep factory grease inside the rollers.

Signs It Is Time to Replace the Chain

The adjusters are at or near the end of their travel.
You can pull the chain away from the rear sprocket at the back and see more than half a tooth.
Tight spots that do not go away with cleaning and lube.
Sprocket teeth look hooked or sharpened like a shark fin.

Replace chain and both sprockets together. A new chain on worn sprockets wears out far faster, so the saving is false. If you are still learning what parts cost to run, the advice in choosing your first motorcycle as a new rider covers running costs beyond the purchase price.

On the Road and Before a Trip

Before a tour, check tension and condition the week before, not the morning you leave, so there is time to order parts. Pack a small can of lube and a rag. On a multi day ride, a quick lube every second evening is plenty for dry weather. If you are planning mileage for a longer trip, our guide to how many miles a day to plan on a motorcycle trip helps you build in those stops.

FAQ

How often should I check motorcycle chain tension?

Every 500 miles or every couple of weeks for regular riders, and before any long trip. New chains stretch fastest in the first few hundred miles, so check those more often.

Can I use WD40 as chain lube?

It works as a cleaner and water dispersant, but it is too thin to protect the chain on its own. Follow it with a proper chain lube.

Does a loose chain cause it to come off?

It can, if it is very loose and the sprockets are worn. A chain within the manufacturer's range on healthy sprockets will stay on.

Ten Seconds That Save a Chain

Make the push test a habit every time you fill up: lift the lower run, check the slack, and look at the sprocket teeth. Keep it within the manual's range, on the loose side rather than the tight one, and lube a warm chain every few hundred miles. More riding know how is in our motorcycles section.