A motorcycle chain is an important element to the machine; without it, you wouldn’t be able to move your motorcycle much. But it can be completely frustrating when you do perform regular maintenance on it and it still acts up. Many people run into the problem of the chain constantly becoming loose without a solid answer as to why.
Why does my motorcycle chain keep getting loose? A motorcycle chain that keeps getting loose is usually caused by the rear axle or chain tensioning bolts not being tight enough. It can also be cause by a new chain not being worn in enough, worn down sprocket teeth, having too tight of a tension, or having the wrong size of chain installed.
It’s important to fix the issue if you are constantly running into a loose chain on your motorcycle. Having run into this problem many times myself, I can explain everything you need to know about finding the reason it’s becoming loose and how to stop it from happening again.
Reasons For A Loose Chain
There are several reasons that can cause a motorcycle chain to become loose over and over again. There are a few simple ways to check how it’s happening that shouldn’t take much time at all.
At first, a new motorcycle chain will become loose because it has the ability to “stretch” a little bit. It’s not the metal itself that stretches, rather in between the links there’s a little bit of slack. As those links turn, they wear into each other; they’re brand new and the metal isn’t quite worn in yet.
The wear between each link is minuscule. But because there’s an average of about 100 links in a chain, all of that wear combined can give the impression that the chain has stretched and you’ll likely notice some slack on your new chain after a few hundred miles. After you get a new chain, ride it for about 50 miles and check the chain tension. Tighten it up again if needed.
If you haven’t recently gotten a new chain and you notice it still becoming loose, there is one common culprit (especially among older motorcycles). The rear axle for the rear tire slides through two fork shaped parts that point backwards on the back of the swing arm. Your axle rides in the middle of those two forks.
There is a bolt on either side of the rear wheel; as you tighten down that bolt, it pulls the rear tire back. Many times, if your chain keeps getting loose, it means the axle or those chain tensioning bolts are not tight enough. This is the cause of a loose chain 90% of the time.
If the teeth on the front sprocket or rear sprocket (or both) are worn down, it can also cause a chain to become loose. Since there’s less surface area going in between the links to spread them out, the chain will appear to have become stretched. This is more of a one time occurrence, but checking in on the teeth of the sprockets is always a good idea if this is happening to you.
Each chain requires a little bit of slack in it. That’s why it’s important to check the tension of the chain to ensure it isn’t too tight. If you’re over tightening the chain, the chain is going to keep “stretching,” or wear into the links more aggressively. Check with your owner’s manual and make sure you aren’t over tightening your chain as every motorcycle is different with how much tension it needs.
Chains on motorcycles are not interchangeable. Each motorcycle calls for a specific kind and size of chain to fit correctly; the chain needs to fit over every tooth of the sprocket. If it doesn’t fit perfectly with the sprocket teeth (such as if any of the links sit on top of the teeth), you have the wrong chain.
I have seen this problem personally. I bought a chain off of eBay once and it had the wrong teeth spacing for the sprocket. It fit around almost 3/4 of the sprocket with just a few teeth that didn’t fit between the links. If you notice this at all, replace your chain with the right one. This could potentially cause the chain to slip off altogether.
How To Fix A Chain That Keeps Getting Loose
Luckily, fixing a constantly loose chain on a motorcycle is relatively simple, even for the least experienced mechanics. Once you’ve found the reason your chain keeps getting loose, try one of the following methods to fix it.
If you recently got a new chain and it still seems to become loose after the 50 miles, ride another 50 miles and tighten it accordingly. Each chain is different and it may require a few hundred miles for it to “stretch” into it’s normal state. There’s a lot of play in the rear chain adjustment so even if your chain is still working on wearing into those links, you’ll have room to add more tension.
Your likely culprit, though, is that the rear axle or tensioning bolts aren’t tight enough. These bolts have to be torqued to a certain tightness, so again you’ll need to refer to your owner’s manual to see exactly how tight the axle and bolts need to be.
Sometimes, through the constant vibration of the motorcycle, the tensioning bolts can become a little loose over time which will give slack to your chain. Try putting a lock nut on there to prevent those bolts from becoming loose, especially if you have a motorcycle that vibrates a lot.
You’ll obviously need to replace one or both of the sprockets if you’ve notice the teeth have worn down. Even if it’s just a few teeth that have worn, that can create a ripple affect and cause the other teeth to wear down much faster, so it’s best to simply replace it.
If you have tried all of these methods and your chain still seems too loose, it may be time to buy a new chain because it’s probably worn and stretched too much. Changing a chain is actually a pretty simple task.
On most chains, there’s one link on it called a master link. There’s a little clip on there that you have to pop out and will make the chain separate. The front sprocket is pretty hidden, but there’s usually a few teeth exposed that you can feed the new motorcycle chain on to which will come out the other side when rotated. Once you feed that through, you can connect the chain together by putting the clip on the master link.
If you have a motorcycle that does not have a master link, you’ll have to cut the chain off with either a grinder or you can take the rear wheel off. You’ll need to take the rear wheel off to put the new one on anyway.
I have created an entire video series about how to restore a motorcycle from start to finish. Within this series includes in-depth tutorials about removing, replacing, and putting proper tension on the chain. Also included are tutorials on hard to tackle components such as body work, carb rebuilds, and electrical. Click here for more information if you’re interested in restoring or building your dream motorcycle!
Maintenance And Prevention
Having to deal with a motorcycle chain that keeps coming loose can be a pain. Performing regular maintenance on it will help ensure the prevention of this annoying occurrence.
Once you have fixed your chain, it’s important to continue checking it every few hundred miles to make sure it still isn’t becoming loose. Try checking it about every other time you fill up with gas.
Make sure it has the right tension. Each motorcycle is different with how much tension is required on the chain, but in general most bikes require about a half inch of slack. But again, check in your owner’s manual to check how much slack your specific motorcycle needs on it’s chain.
Be sure to lubricate the chain about every 4,000-5,000 miles or every six months, whichever comes first. I always check my chain every time I change the oil since that has about the same intervals of maintenance.
Consequences Of A Loose Chain
A loose chain has the potential of coming off the sprockets altogether. This means you’ll lose power to your motorcycle even though the engine is still running. This may not seem so bad unless you think about losing power in the middle of the freeway.
A loose chain also has the potential of breaking and either slapping the back of the rider’s leg or projecting backwards and damaging the vehicles behind. Or it’s possible for it to jam up in one of the sprockets and cause the motorcycle to abruptly stop. See my article here to learn more about what can happen if a motorcycle chain breaks.
Paying attention to the chain on your motorcycle is important. It’s a small and simple part, but if left unchecked it can be quite a nuisance for the motorcycle owner.