Advice: How to adjust a chain

Chain adjustment on your motorcycle is a very simple task, but one which is overlooked by many.

Having a correctly adjusted and lubed chain will make your motorcycling life easier. It will not only make for a much quieter experience, but more importantly will reduce strain on other parts of the motorcycle.

A chain that’s too loose can jump off the rear sprocket, causing lots of damage to the bike, but also to your health if it gets jammed. That’s an extreme case, but loose chains also wear grooves into your swingarm and engine cases.

A chain that’s too tight limits suspension movement, and also causes undue strain on things like countershaft and wheel bearings. On some motorcycles, it’s imperative you have the chain adjusted correctly. Ducati models with the swingarm bolt going through the crankcases, for example, can be susceptible to cracked crankcases from chains which are too tight. Be warned.

In other words, a chain that’s too loose will flop around and damage anything in its path, while one that’s too tight will wear out interacting parts much quicker than normal and stop your rear shock from working properly.

Getting it right
We are using our trusty Yamaha MT-10 here to demonstrate the correct techniques – which if followed correctly will let you adjust the chain on just about any bike. The exemptions are bikes with a single-sided swingarm or a classic with an eccentric adjustment setup.

Most owners’ manuals have the required chain slack listed in them, and the MT-10 manual lists 20-30mm as the desired chain slack. This is just an example of course, and if you have an older bike and can’t seem to find any information on drive chain slack, then the 20-35mm is a good rule of thumb.

As a general rule, you check the chain tension with the bike sitting on its wheels, or a bike stand, so it has its own weight on the rear suspension – but not the extra weight of a rider.

There are tools on the market that can help you determine chain slack, but the trusty tape measure is as good as any.

We found it easier to put the MT-10 on a race stand, but if that’s not an option the sidestand is fine.

We’ve backed off the chain tension so it’s too loose. You can see from the photos that it’s 55mm. Way too loose. Make sure you hold the rule in the same spot when measuring the chain slack so you don’t get a false reading.

We use a 27mm socket on this bike to loosen off the rear axle nut – not right off, but just enough to loosen it. We can then use the 12mm spanner to adjust the bolts on either side.

Now rear wheel and chain alignment is important, so the bike runs true down the road and doesn’t unduly wear the chain and sprockets with misalignment.

Alignment marks
There are a number of ways to make sure the rear wheel is in line with the front wheel, but the simplest way is to use the alignment marks on the adjuster and the swingarm. They must line up with corresponding marks on both sides. Manufacturing tolerances sometimes have the alignment marks slightly off from each other but this is usually minimal. In 99.9 per cent of cases they are fine and within acceptable tolerances.

Once we’ve adjusted the chain to the correct tension (we’ve set it right in the middle at 25mm) and the alignment marks are the same on either side we can tighten up the rear axle nut.

The easiest way is to use a rag or a screwdriver to tighten the chain on the rear sprocket while we nip the axle nut up to the correct torque as per the manufacturer’s settings. You can find these torque settings in workshop manuals or even online. If you don’t have a torque wrench handy then make sure you do it up tight.

Regularly checking your chain tension is a handy habit to get into. It also allows you to get into the habit of looking over the bike for any other issues that may become apparent. And while you are there, put some quality chain lube on it!

This article was originally published on February 26, 2018.