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Common Tread

How to determine when your motorcycle chain and sprockets need to be replaced

Jan 28, 2020

I’ve owned a lot of chain-driven motorcycles over the years and I also maintain all of RevZilla’s house and press bikes. This means that I take care of a lot of chains. I habitually inspect the chains on all of these machines to ensure they will happily propel me and my colleagues down the road or trail without any trouble.

We've published lots of information about caring for your motorcycle's chain, from our article on how to clean and lube it to our video on how to adjust your chain. You might also want to see our article explaining why chains are the most common form of final drive and our piece on other odd facts about chains.

At some point, though, every chain needs to be retired, and that raises another question: How do you know when your chain and sprockets should be replaced? This article will help you determine if it's time.

Rusty chain, binding links and overly pointed teeth are all obvious visual signs that these components need replacing. Photo by Joe Zito.

How to inspect a motorcycle chain

Fortunately, chain drive components are easy to visually inspect on most bikes so it shouldn't take long for you to determine if you need to buy a new chain and sprockets. ProTip: This job may require getting your hands dirty, so it might be a good idea to grab some gloves before inspection. A bright flashlight really helps, as well.

Your service manual will probably provide a procedure for determining how worn the chain is by hanging a weight on it and measuring the length of a specified number of links.

KTM suggests checking for chain wear in a slightly more complex way. Image from KTM service manual.

Another, much easier way to check for a worn chain is to try to pull the chain away from the rear of the sprocket on the rear wheel. If the chain is worn, you'll reveal about half a tooth of the sprocket. A new chain will wrap around the sprocket snugly and won't pull away.

The service manual for my 1970 Yamaha shows a more traditional approach for checking chains and sprockets for excessive wear. Photo by Joe Zito.

Pulling the chain away from the rear sprocket like this is an easy indicator of worn-out parts.

Other things to look for are binding or kinked links that cause tight spots (put the bike on a rear stand or the center stand, if it has one, and spin the rear wheel to see if the chain maintains the same tension). Also, look for excessive rust.

Examine the sprockets, too. Look for sprocket teeth that are hooked, pointed or chipped.

The front sprocket on my '70 Yamaha showing some wear. Photo by Joe Zito.

You can see the difference between the worn and new rear sprockets for the Yamaha. Photo by Joe Zito.

If you've followed our advice in the articles and videos above about cleaning, lubing and adjusting your chain, you may find your chain and sprockets still have plenty of life left. Personally, I suggest cleaning and lubing street bike chains every other tank of fuel and more frequently on off-road bikes or after riding in wet weather. Chain tension is also very important. Too tight puts a ton of stress on your transmission bearings and seals, as well as accelerating the wear of the chain and sprockets themselves. Adjust your chain tension as recommended in your manual or by the sticker on your swingarm or chain guard.

Even the most pampered chain won't last forever, though. So if you've determined it's time for a new chain and sprockets, now what?

Replacing your motorcycle's chain and sprockets

While replacing chain drive components is a job most people can tackle at home, you have to have a way to securely lift the rear of the motorcycle to remove the rear axle and wheel. So if you lack that, it may be worth having a local shop do the work for you. One thing to consider, if your bike is due for a rear tire soon, having the shop replace your chain and sprockets while they have the rear wheel off could save you some labor costs.

Joe loves wrenching on old bikes, especially when they have a factory center stand like this '70 Yamaha R5. Photo by Roy Kim.

If you do the job yourself, determine the parts you need to order. It's never a bad idea to replace the chain and both sprockets as a set, but if you've stayed on top of chain maintenance, it's possible you could save some bucks and not have to replace both sprockets.

For example, my 2018 KTM 250 XC-W chain was nearing the end of its life. The rollers were loose on the rivets and I was just starting to be able to pull it away from the rear sprocket a little bit. Since I caught this early, I only needed to replace the front sprocket and chain. The rear sprocket was showing no signs of wear, but you can see how the front sprocket is showing some wear in the photo. Irregular looking teeth that are hooked or sharp means that the sprocket is toast. Also, the valleys between the teeth should be a constant radius, without a “flat” area.

The front sprocket on my KTM was just starting to show a little wear. Photo by Joe Zito.

My 2018 KTM with a new chain, front sprocket, slides and guide installed. Apparently gold chains add horsepower, so I had to get one, of course. Photo by Roy Kim.

To give you the opposite example, last year Editor Lance replaced the chain and rear sprocket on one of his bikes, but kept the same hardened steel front sprocket because it looked OK. Unfortunately, the bike made a god-awful noise as the new chain meshed poorly with the worn sprocket. He quickly replaced the front sprocket and the noise disappeared.

Cost

If you do need to replace both sprockets and the chain, what's it going to cost you? It really depends on the motorcycle you're working on. Chains can range in price from $20 for a plain chain for a small, lightweight motorcycle to over $200 for something like a quality O-ring chain for a bigger, more powerful bike. O-ring chains have lubrication built into the links, held in by rubber O-rings between the side plates. The O-ring chains cost more but also last longer.

Front and rear sprockets cost anywhere from $50 to over $250 a set, depending on size, materials and their expected lifespan.

If you're doing the job at home, you'll also need a chain tool to "break" the old chain (pushing out one of the rivets) and riveting the new chain, unless you're using a clip-style master link. A chain tool will cost somewhere between $40 up to around $90, but with luck you only buy one once and use it for years.

Replacing your chain and sprockets gives you a great opportunity to clean everything up nicely. Photo by Roy Kim.

Additional chain drive information

Next, check your manual to make sure you know what size and length of chain to buy. You'll see common sizes such as 520, 525 and 530. The first number refers to the pitch of the chain. This is the distance between the rivets in eighths of an inch, so the “5” means five eighths of an inch. The other two numbers refer to the width of the chain roller, or distance between the inside of the inner plates, also in eighths of an inch, so “20” equals 2.0 eighths or a quarter of an inch. The chain width should always match the sprocket width.

One of the advantages of chain drive over other forms of final drive in motorcycles is that chains and sprockets make it easy to change the overall gearing. For example, if you feel your motorcycle is "screaming" at highway speeds, you can increase the size of the front sprocket by a tooth or decrease the size of the rear sprocket and the engine will be turning slower at a given speed. The tradeoff is you'll lose some acceleration. Going the other way will increase acceleration. If you fit a larger sprocket to either end, just make sure you have enough clearance. In any case, you can always use the stock sprocket sizes when buying new ones.

Other parts to consider replacing

While you're doing this job, your motorcycle may have some other components you should check. Chain sliders, for example, are easy to neglect because they are usually black and covered in grime. They are those rubbery pieces that keep the chain from dragging on and sawing through your very expensive swingarm. Off-road bikes with lots of suspension travel usually have other pieces, such as upper and lower sliders or rollers and possibly a lower chain guide, to help keep chain tension right. Check them for wear while you're checking your chain and sprockets.

The factory KTM manual shows what to look for when considering replacing your chain slider. Image from KTM manual.

On very old or high-mileage bikes, it also pays to check the cush drive rubber dampers while you have the wheel off. These rubber pieces in the rear hub reduce abrupt driveline forces.

On older bikes, it is a good idea to check or replace the cush drive rubbers in the rear hub. Photo by Joe Zito.

The bottom line is that the more often you check your chain, clean it and lube it and adjust the tension, the less often you'll have to do the bigger job of replacing it. Follow the steps above and your drive chain can last many miles.

I enjoy sharing these tips with you! Please let me know if you folks have any other "how-to" articles you would be interested in and I'll do my best to get them together for you.