motorcycle chain on a 2012 Triumph Daytona 675R

Every motorcyclist has a “least favorite things to do” list, and at the top of that list is undoubtedly the task of cleaning and lubricating the chain. No one likes to think about it… but we should, because without your chain, your motorcycle is just a very heavy bicycle. 

Chain drives are still the most popular power transmission system fitted on motorcycles today, even with belt drives and shaft drives also playing dominant roles in final drive power transmission. Belt and shaft drives have some major disadvantages compared to chains, which are lightweight, robust, easy to fit and adjust, highly efficient and cheaper to install and replace. 

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We will take a closer look at the modern motorcycle chain, how it works and why maintenance is important, and what to think about when it comes to chain lubrication in this three-part series. First up, let’s talk about how chains are constructed and what factors make them wear out. 

CHAIN COMPONENTS 

A modern motorcycle chain consists of approximately 500 pieces and is responsible for the power transfer from the gearbox to the wheel. While they are an essential component, motorcycle chains lead a very unglamorous life and are often neglected. But after you delve deeper into the mechanics of chains and sprockets, you will realize they’re incredible and see how important they are for your bike. 

Chain link assembly

A chain consists of combinations of inner links and outer links. The power from the engine is transferred where inner and outer side plates are connected by the pin. While the pin is connected to the outer plate, the bush is connected to the inner plate. This contact point between pin and bush needs to be lubricated for the two parts not to wear. 

Before the introduction of sealed chains, motorcyclists had to constantly strip down the chain from the bike and cook it in a grease pan before hanging it up to dry. This would allow the lubricant to reach the inside of the chain, the pins and bushings, where it was most needed. It was a filthy job, and a real time-suck when you just want to go out for a quick ride. 

Luckily, modern motorcycle chains are equipped with O-ring (or X- or Z-ring) seals. These seals are intended to keep a lubricant sealed inside the chain, between the pin and bush, exactly where it’s needed, and keep dirt and grit out of this important contact area. The lubricant is sealed in for the entire life of the chain and does not need to be changed. 

Modern sealed chains can last a long time. Possible reasons for chains to be replaced include quality issues, physical damage to the chain or just physical wear and elongation of the chain past the point of adjustment. However the main reason for modern chains to fail is the loss of seal integrity 

WHY AND HOW DO CHAINS WEAR?

In an ideal environment chains can last almost indefinitely, but motorcycle chains operate in hostile environments. Not only do rain, dirt and salt attack the chain, but the constant shifts in power and gear changes also put a huge strain on the chain, necessitating the inevitable replacement of  motorcycle chains and sprockets.

You probably know that chains need proper lubrication at regular intervals to function properly and to prevent wear. But even when maintenance is carried out regularly, chains still wear and chain adjustments still have to be made, pushing the rear wheel further and further back to take up the slack of the chain. 

So how do chains actually wear? 

First of all, chain wear is normal. However correct maintenance can reduce chain wearing factors and dramatically increase chain life. 

Often you hear people saying that their chain ‘stretches’ and that by adjusting the chain tensioner this stretch is taken out. Actually, it is not true that a chain gets longer in the sense that material stretches. When you compare a worn chain against a brand-new chain it will be difficult to see a difference until you put them under a load. Suddenly the worn chain will be longer than the new chain. 

Chains wear at the point where inner and outer side plates are connected by the pin. While the pin is connected to the outer plate, the bush is connected to the inner plate. Through the rolling action of the chain, pin and bush constantly rub against each other. If this contact point is not sufficiently lubricated, the pin will wear into the bush, thus allowing it to sit deeper in the bush. As this usually happens over many links, the chain physically becomes longer, up to the point where adjustment is no longer possible. 

Proper chain pin-to-bush position (above) vs chain "stretch" (below)

A chain will also fail quickly if just one chain link is subject to excessive wear, possibly due to a quality error or lack of lubrication. As the saying goes, a chain is only as strong as its weakest link. 

Your chain and sprockets rely on a delicate interplay to transfer power efficiently. If just one chain link elongates, this link will bear the entire load of the chain as it articulates around the sprocket, instead of sharing the load among all the chain links being in contact with the sprocket. This is called a spacing issue. Both chains and sprockets have pre-defined spacing to match each other. The chain pitch is the distance between valleys of the sprocket teeth. If one chain link wears, it changes its spacing and becomes mismatched to the sprocket. 

Sprocket position: Good chain spacing (yellow) vs. bad spacing (orange)

Due to the different spacing, the other links will not actually make correct contact with the sprocket teeth. As the chain wears, the spacing increases and the chain rides higher on the sprocket teeth, causing them to wear. The sprocket teeth often start to shape into a wave pattern. This causes chain and sprocket to wear unevenly. In an attempt to balance out the chain stretch, the sprocket wears and adapts to the new spacing of the chain, which in turn will accelerate the stretch of chain links that are not yet worn. 

Usually chain wear is not a linear function that can be measured and calculated. If one link starts to wear and “stretch,” chain wear is accelerated throughout the chain and follows an exponential curve. Hence sprockets should also always be replaced when a new chain is installed, even if the sprocket seemingly shows no signs of wear. If a new chain is installed on an already worn sprocket, the chain will wear quicker as it tries to adjust to the existing wear and spacing pattern on the sprocket. 

Overall, chain wear is affected by a variety of factors: 

  • Riding conditions and other environmental impacts 
  • Chain tension 
  • Riding style and type of motorcycle engine 
  • Quality of chain and sprockets 
  • Other factors such as quality issues, mechanical impact or tampering, etc. 

Chains can last a long time when they are properly looked after. In the next part of the series we will take a closer look at chain lubrication, what to do and what to avoid, and how you can maximize your chain life and minimize money spent on replacement parts. 

Matt Ennen (@matthias) started riding 11 years ago in India with a Royal Enfield Bullet 350. Having subsequently fallen in love with the world of motorcycles, he managed to find a job in the industry and spent his first paycheck on a Honda CB500, leaving him with no money for rent or food and forcing him to confess to his parents. SInce then, many bikes have come and gone, and he is now the Marketing Manager for Scottoiler, a manufacturer of automatic chain oiler systems. 

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Suggested vendor: Scottoiler Ltd

The Scottish solution to chain lubrication

Chains need cleaning, lubing and adjusting. Spray-on chain lubes use high amounts of tack additives and do a great job of attracting abrasive dirt. This gritty paste accelerates wear on your chain and sprockets. Fact. Scottoiler automatic chain lubrication systems constantly lubricate your chain with specially developed low tack oils while you ride. This means no more filthy grinding paste build-up and significantly fewer chain adjustments. With a Scottoiler chain oiler, chain and sprockets wear at a much lower rate. You'll also experience smoother power transmission to the rear wheel as a result of a well maintained chain. Scottoiler systems are designed for those riders who take a genuine interest in the efficiency and operation of their motorcycles. So if your ride a sport bike, tourer or adventure bike with a drive chain; spend more time in the saddle, not on your knees and let Scottoiler take over your chain maintenance. Scottoilers are made in Scotland, UK to exacting standards since 1985. With over 400,000 sold, they're a well respected product in Europe and are available in the USA from our Pennsylvania distributor. "We've ridden from London to Mt. Everest Base Camp so far and with the Scottoiler chain oiler on the bike, we have not even adjusted the chain once" KEVIN SANDERS, GLOBEBUSTERS.