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This is an easy task but there are a few important things you should know when learning how to change the chain and sprockets. The first thing you should always do is change the chain and sprockets at the same time. Chains stretch and sprocket teeth wear thin and lose shape. Fitting only one new item will cause it to wear out faster than it normally would as the parts won’t interlock or fit together properly.
- Start by removing the front sprocket. You need the chain on to do this as it offers resistance when you attempt to loosen off the sprocket nut. Have someone apply the rear brake at the same time that you loosen off the nut using a large socket.
- Some bikes have a circlip which needs removing first. My YZ250 has this lock washer in place, which needed the ‘flaps’ to be straightened out using a small screwdriver.
- Now take off the chain. Some chains have a removable connecting link (as shown here) that you can remove with a pair of long nosed pliers or a screwdriver. If it is a fixed or solid link you need to bust out the angle grinder or chain breaker to remove it.
- Remove the rear wheel and swap the sprockets over. All you’ll need for this is an allen key and a spanner.
- Reassemble the rear wheel.
- Slide the new front sprocket on and finger tighten the nut as you won’t be able to tighten it properly until you put the chain back on.
- Feed the new chain through the front sprocket all the way around ready to join. Chances are you’ll need to shorten the chain. This is where you need to be very careful! The links need to be removed in two’s (male and female connecting parts). If you shorten it too much – there’s no going back and you will need to buy another chain.
Line the chain up with the chain adjuster bolts wound in and take a look at where the best join will be. You don’t want the chain to be too tight once it’s on so you’ll need a little bit of slack that you can take up with the adjuster bolts.
To remove the links you’ll need a chain breaker (a specialized tool) or an angle grinder to grind away the burred end of the joining pin.
Once you’ve done that, connect the chain using the joining link. Make sure the clip that secures it has the rounded end facing the direction of the drive. This prevents the possibility of something snagging the clip (while riding) and tearing it off.
If you are using a solid link you’ll need to get someone to hold a mallet or hammer on the backside of the link while you use a hammer and punch to roll over the ends of it (the same way the rest of the links are secured). Make sure you do this correctly otherwise it won’t hold! If you haven’t done this before it’s probably a good idea to watch someone who has.
- Apply the rear brake again and tighten the front sprocket. Fold over the lock washer – or re-secure the circlip, and tighten the chain adjuster bolts.
Now you’re ready to roll! Here’s some more information on how to adjust and maintain your dirt bike chain and sprockets.