Last updated on June 1st, 2019
Next to tire pressure and chain lubrication, motorcycle chain adjustment is among the most ignored simple maintenance tasks. Even though chain tension (slack) and rear wheel alignment is a major factor for the longevity of both the chain and tire. Not to mention the motorcycles handling, as well as basic safety. To see what happens when a motorcycle chain falls off due to neglecting it, see a short video. The saddest part is that it could have been totally avoidable with less than an hour of time and a few tools following this process.
Here we’re going to go over basic motorcycle chain adjustment. That is, how to check the chain slack and adjust chain tension, as well as align the rear tire. We’ll be working on a 2017 Kawasaki Ninja 650 ABS. It would also be exactly the same process on the 2017- Kawasaki Z650.
On most modern bikes, the process is extremely similar. So, regardless of what bike you ride, you should find some value in this tutorial.
Tool Requirements: Basic-intermediate
Time: 1 Hour
How often do we have to tackle motorcycle chain adjustment?
Per Kawasaki’s enginerds, the chain slack should be checked (and adjusted if necessary), every 600 miles. You should check the rear tire alignment simultaneously, and adjust if necessary.
There are those that would recommend you check it before every ride (at least visually), but that’s way too often for most people in practice. The good news, however, is that while you really should check it about every 600 miles or once a month, you will rarely have to adjust it. And to check it, it only takes about fifteen minutes, so don’t procrastinate. Remember, the alternative.
Also worth mentioning is that the most important time to check the chain tension and rear tire alignment is during the first 500-1000 miles of the bike. That’s when the chain will suffer its initial (and most significant) stretch. This is one of the important things the glorified ‘first service’ should take care of – which I totally recommend you save the coin and do yourself.
Moral of the story is check it often, adjust it sporadically, and don’t forget about it.
What you’ll need
Motion Pro Chain Slack Setter or a Ruler
With all routine maintenance tasks, doing the work yourself (in lieu of a mechanic) will save you time and money. That makes it worthwhile, both time-wise and economically, to get any tool that makes the job easier or quicker. This is one of those tools. Checking chain slack with this is much, much quicker and easier than using a ruler. Plus it gives you much more consistent results. For the price it’s a no brainer for any motorcycle owner. However, in a pinch a regular foot long ruler can work just as well.
There are many ways to check chain alignment, however the best, quickest, and easiest method I’ve found so far is this tool. Other options are simply to use the hash marks on the frame, string, or tape measure. But for doing it on a regular basis, nothing beats its precision and speed.
Other Tools & Supplies
- 1/2″ Drive Torque Wrench – To set the right torque on the rear axle nut.
- Breaker Bar – To break loose the rear axle nut.
- 1/2″ Socket Drive Ratchet – Needed to apply counter torque to the axle when loosening or tightening its nut.
- 22mm and 27mm Socket – For the axle nut and axle bolt head, respectively. Be aware that these sizes are typically not included in normal ratchet kits.
- Pliers – To remove the cotter pin on the rear axle nut.
- Cotter Pin – 4.0x35mm – To secure the rear axle nut. It isn’t ideal to reuse the original cotter pin, but in a pinch you can do it. The OEM size per Kawasaki is 4.0x35mm. It’s part 550AA4035 at around 3$ per pin. But any similarly sized cotter pin can be used. Typically it’s cheaper and more worthwhile to just buy the kit and use the size you need, keeping the rest as spares.
- Allen (Hex) Key Set
Note for the Kawasaki Ninja 300
If you’re performing this DIY on a 2012-2017 Kawasaki Ninja 300, the 22mm and 27mm sockets are not needed. The Ninja 300 uses 17mm and 24mm sockets, respectively.
Motorcycle Chain Adjustment – Step by Step
Step 1 – Put the bike up on a rear stand
For this job, I’m going to use a rear stand, which attaches to the spools. If you don’t have rear spool sliders already, then now would be a great time to get them. Luckily they’re cheap and can be installed in seconds. Plus, in theory they also work as frame sliders.
One note though. There is controversy on whether the chain slack should be checked on the sidestand or a rear stand. In either case the swingarm is loaded, so both I and a majority of motorcycle owners check and adjust the chain tension while on a rear stand. Mostly for convenience and speed.
Pro-Tip – Mark the chain with a permanent oil pen
On the 2017 Kawasaki Ninja 650 there isn’t any differently colored master link on the chain. I recommend marking the chain with a permanent oil pen so you know where you started and where to end when lubricating the chain. Plus, they’re perfect for touching up paint scratches and chips.
Step 2 – Measure the initial chain slack
The first step is to measure the initial chain slack. The correct chain slack (for this bike) is 20-30mm when measured roughly at the middle of its length. In this case we measured 35mm which is out of spec and too loose.
Keep in mind that if you measure a value between 20-30mm, the chain slack is correct and you don’t have to do anything. That sure cuts short the motorcycle chain adjustment! When the manual says “check every 600 miles”, you should really do so because most of the times it’s only checking. In practice you probably won’t have to adjust your chain more than every 2-3k miles. So, if you get a value that’s well within spec, skip to step 13.
I personally used a Chain Slack Tool because it’s a lot easier than fiddling with a ruler. Anything that makes you more likely to keep on doing a routine maintenance task is worth it, and this is one of them. Simply hold the top of the tool against the bottom of the swingarm, put the yoke around the chain, and move the arm up and down. Remove the tool and read the value.
Take care if you’re using a ruler to measure chain slack
If you’re using a ruler, remember that you have to measure at the same point of the chain link. Either top, center or bottom – Choose one and stick with it. This means that you want to measure from the top of the link (for example) when pushing the chain up, and at the top of the link when pushing the chain down. It’s tempting to measure at the top when it’s up and at the bottom when it’s down, but this would be the wrong way to measure it. Take a look at the diagram above if this is unclear. One reason why I use the chain tool is to avoid this issue altogether.
Step 3 – Remove the chain and nut cover
Now that we know we have to adjust the chain tension, let’s begin the prep.
Don’t skip this. Take a moment and remove the rear chain cover to make your life easier as well as reduce the risk of scratching it when removing the cotter pin (guess how I know). All it takes is two easily visible and accessible allen bolts.
Also, remove the rubber cover on the axle nut. I’m not sure if Kawasaki intends that to stay there (I believe so), but I have no idea why.
Step 4 – Remove the cotter pin
Now we have to remove the Cotter Pin. The OEM pin is very strong and stiff so be careful to not let your pliers slip when pulling it out and bang something delicate. The trick is to bend it as straight as possible, until it can easily be pulled out. Or you can just cut it with some cutting pliers.
Step 5 – Loosen the rear axle nut
To begin the motorcycle chain adjustment we have to loosen (but not remove!) the rear axle nut. We will need a 27mm socket for the nut side, and a 22mm socket for the bolt head side. Be aware that these are not typical sizes and are probably not included in your standard socket set.
Keep the bolt head secured in place with one hand, and loosen the nut side. Don’t do the opposite, namely try to remove the bolt side with the nut held still. This is because then you’re rotating the entire axle, which is simply unnecessary.
Though this can be done with wrenches and small ratchets, 6 point sockets (opposed to 12 or more) and a long breaker bar make the job much easier. It also reduces the risk of damaging either the bike or yourself.
You only want to loosen the nut enough to be able to rotate it freely by hand. Also, don’t remove it completely.
Step 6 Adjust the motorcycle’s chain slack
To adjust the chain slack we need a pair of 12 and 14mm spanners. While holding the big nut steady with the 14mm spanner, loosen the 12mm nut. Once the 14mm nut is free to move, tighten it clockwise in one-quarter to one-half rotations measuring the chain slack constantly until it tightens up to around 25mm of chain tension. This taking for granted the chain was too loose.
Once the chain tension is properly set, hold the 14mm nut steady and rotate back the 12mm nut until they both lock together. You don’t need threadlocker given how both nuts secure each other, but you can apply it if it makes you feel better. Sometimes I do.
Typically, during routine motorcycle chain adjustment I tend to find that the chain tension is too loose. As opposed to finding the chain too tight after several hundred miles. But that doesn’t mean that sometimes you won’t find it so. If that’s your case, loosen up both nuts and give the rear tire a push forward. Do it while holding the bike and rear stand steady. This will loosen the chain (increase chain slack). Then simply proceed as above for loose chains.
Step 7 – Adjust the rear wheel alignment
Whenever you loosen the rear axle nut, you should check and readjust the rear tire alignment. This means that any time you adjust the chain tension you will have to adjust the rear tire alignment. And vice-versa applies, too. So basically it’s an integral part of motorcycle chain adjustment.
There are many ways to adjust alignment, with the easiest being simply using the hash marks on the swingarm. However forums abound with comments about how the swingarm’s marks aren’t precise, so I like using a specific tool. For quick and painless checking on a routine basis, I use a Chain Alignment Tool. I’m sure a nice gadget like a Laser Chain and Belt Alignment Tool would be even better, but for the price it’s not worth it. One benefit this tool has over measuring tape is that you can quickly look at it at any moment. Even mid-alignment adjustment. It sure beats having to stop and take measurements all over again after a quarter nut turn.
How to use the Motion Pro chain alignment tool
To use the tool, first clamp it on the rear sprocket. Then look at how the rod aligns with the chain. You’ll quickly see if the rear tire aligns with the chain or not. And though the rod looks shortish, you can easily align it visually in such a way that it projects against the whole length of the chain. Just make sure you only look at the rod with only one eye open to avoid parallax errors. In any case it make motorcycle chain adjustment easier.
Similar to how we just adjusted the chain tension, play with the nuts on the right side of the swingarm end to adjust the rear tire alignment. Constantly check the alignment to make sure you haven’t gone too far. Once you’re satisfied with the alignment, measure the chain tension again just to make sure you haven’t messed up its value. Then get ready to torque up the rear axle nut. It isn’t necessary to remove the sprocket alignment tool just yet, though.
Step 8 – Torque up the rear wheel’s axle nut
The correct torque for the rear axle nut is 108 N·m (11.0 kgf·m, 80 ft·lb). You really should be using a torque wrench for this, honestly. But if not, it translates into pretty darn tight. It’s the same torque that is typically applied to a car’s lug nut. As before, we want to hold the bolt head steady while tightening the axle nut.
Once we have brought up the axle nut to the right torque, we have to tighten it a bit more. Tighten until the hole in the axle aligns with one of the grooves in the nut.
Step 9 – Recheck the motorcycle chain tension and rear wheel alignment
Sometimes during tightening things can go a bit whack. You always want to double-check chain tension and tire alignment one last time after tightening the rear axle. Just in case.
Step 10 – Install the cotter pin and covers
We’ve almost finished the motorcycle chain adjustment. Now that we’re sure that everything went well, install a new cotter pin and put its cover back on. When possible, avoid reusing cotter pins.
The final step is to apply some threadlocker to the two allen bolts we removed previously. Then you can finally bolt the chain guard on.
That’s it! The motorcycle chain adjustment is finished. Wasn’t that hard, was it? With this you’ll save plenty of time and money in the future. Given the frequency, it’s certainly a maintenance item worth taking care of yourself. And now you know how thanks to some random bloke on the internet.
By the way, if you just bought you’re Ninja 650 and you’re still looking around for upgrades, check out my 2017 Kawasaki Ninja 650’s mods list. It’s a list of all the upgrades I currently have on the N650 pictured here. And plenty of them are even easier than doing this motorcycle chain adjustment. You might find something that you like. After all, what’s the point of a motorcycle if you don’t farkle it to death?
Anyway, if you found this interesting, check out what other projects I’ve been up to — here are some you might like: