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Service: Replacing chain & sprockets

Not a hard job.

If you’re at all technically minded, replacing your chain and sprockets is really easy. By using this guide you don’t need to pay your mechanic, if you don’t mind getting your hands dirty.

One of the most basic motorcycle services is changing your chain and sprockets. You don’t need to do it that often, but the job is straightforward, so if you can hold a tool, you’ll most likely be able to do it yourself. In this text I’m using my late Triumph as an example.

How to know when a change is due? Motorcycle or chain manufacturers often have a service limit, this is to say, the length of X amount of links may not exceed Y, but have you ever heard of anyone checking that for a drive chain? No, me neither.

Change your chain and sprockets if:

  • There’s obvious failure in the chain, for instance O-rings sticking out or seized links.
  • Chain is stretched to the extent where you’ll be able to pull it clear from the rear sprocket by grabbing a link an pulling backwards.
  • Sprockets are excessively worn; the teeth are no longer symmetrical.
  • Chain is unevenly stretched, the slack changes as you turn the rear wheel. You might also feel this as a sort of a judder or vibration when riding.
  • Chain slack starts increasing rapidly.
  • Chain noise increases considerably.

It’s very important to replace both sprockets at the same time with the chain, as worn sprockets will hurt the chain life. As the front sprocket has fewer cogs, it’s usually the first one to wear out. Some people advice to replace it every 10 000 km (6 000 miles) to increase the chain life. I used to do that as well, but now I really haven’t bothered, the advantage isn’t clear enough. There’s no harm to do it though. Mind you, do not reverse the sprockets; it will result in accelerated wear.

It will look the same under your front sprocket cover too.

Start out with removing the front sprocket cover. It’s probably filled with grinding paste of chain lube and dirt. Bend down the nut locking plate and open the front sprocket nut. It’s probably pretty tight, so either have a friend to apply rear brake and hold the bike while you wrench it open or use a bolt gun. If you use a bolt gun, make sure the transmission is in neutral; shock load to the gearbox isn’t the best of ideas.

 

Bolt gun is a handy tool to loosen the front sprocket nut.

 

Leave the sprocket on the shaft and cut out the old chain with an angle grinder. You could use a chain tool to cut it, but why bother? It’s not like you’ll be reusing the chain. Just watch where you cut and where the spark spray hits.

 

Yes, the angle grinder is a Kawasaki!

 

Remove the chain and front sprocket. Now it’s also time to lift the bike up on a stand if you haven’t done it already. Remove the rear wheel and with the sprocket carrier still in the wheel, loosen the sprocket nuts while holding the wheel still and remove the rear sprocket.

 

The tyre will give you leverage when loosening the rear sprocket carrier nuts.

 

Clean under the front sprocket cover, the rear wheel and sprocket carrier, rear fork and wherever you might see chain lube deposits. Also check that for instance front sprocket oil seal isn’t leaking, that the wheel bearings and sprocket carrier rubbers are all right and chain slider isn’t excessively worn.

 

Little brake cleaner makes the old shitty bits shiny again.

 

When everything is clean and inspected, it’s time to start putting bits back together. Check that the sprockets match the old ones; usually (but not always) the texts on the sprockets face outwards.

Begin by installing the rear sprocket on the carrier. Usually the nuts are lock nuts, but if not, or if the nuts are worn so that the locking action is questionable, it doesn’t hurt to use a bit of thread-lock. Install sprocket carrier to wheel and wheel to bike, but don’t tighten yet, just leave it on the swing arm.

Then install the front sprocket (with a new lock plate if required) and chain. Don’t tighten the front sprocket at this point. Check the chain length and shorten if necessary. If you’re unsure about the length, it pays off to get as long a chain as possible. Shortening it isn’t that hard, but boy, it’s a bitch to make one longer. Note that the standard length doesn’t necessarily fit, if you change the gearing!

When shortening a chain it’s crucial to remember that you will want two inner links facing each other. Forget this and you could easily end up with a chain that you shortened too much. I find it easiest to have the chain ends meet at the rear sprocket, which allows for sort of checking the chain slack at various axle positions. When you’re happy with what you’ve got, make note of where you’re going to cut.

Take the rivet heads (of the link to be cut) down with an angle grinder, and use a chain tool to push the link out. You can also punch it out, but it’s a bit of a hassle and a chain tool makes your life much better.

 

A chain-cutting tool is nearly essential for shortening a chain.

 

Now it’s time to put the chain ends back to the rear sprocket again. Take the link, install O-rings to the bottom and push the link to the chain ends. Install O-rings and front plate on the other side. Push the plate so, that the joining link is of equal width with the others. Here’s where a chain-installing tool would be really handy, but failing that, adjustable pliers will do the trick.

When that’s sorted, it’s time to rivet the link. Again, really easy with chain-installing tool, but doable by other means too. Use a large hammer as an anvil on the backside of the chain and round-ended riveting punch on the outside. Hit the punch until the rivets’ ends spread out slightly. When you’re all done, check once more that everything is as it’s supposed to and tighten the front sprocket, lock it with a lock plate and install the sprocket cover.

 

I used a DIY-punch made from an old file. Found my riveting tool straight after I had finished.

 

Lower the bike on the ground, adjust the chain slack to manufacturer specifications and tighten the rear axle nut. Now it’s time to go on a test ride and enjoy your new, smooth and quiet chain and sprockets!

 

The final step is to adjust the chain slack.

 

In a while the chain and sprockets will get bedded in, and relatively soon you might expect to have to adjust the slack. After this one, the next adjustment should be thousands of miles away.

 

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