Replacing a worn out chain and sprockets is one of the messier home motorcycle maintenance jobs, but it’s relatively simple provided all the steps are carried out in the right order.
You will be removing and replacing the front sprocket, removing the rear wheel, replacing the rear sprocket, refitting the wheel and finally replacing the chain.
Note that while smaller motorcycle chains are joined by an easily removable/fitted split link, bikes of around 600cc and above are likely to use an endless chain, possibly an O-ring type, joined by a so-called soft or rivet link.
These require a special tool both to split and remove the old chain and to join the ends of the new chain together. Decent quality breaking/riveting/ sideplate press-fitting tools cost from around £40 and are a good investment for the DIY mechanic.
Sometimes the supplied chain might be longer than the original, in which case you’ll need a chain breaker to remove some links whether the chain uses a split link or soft link.
Also bear in mind that front drive sprockets are commonly held on by a large nut secured by a tab washer. If, so a suitable socket and, ideally, a long breaker bar will be needed, along with a new tab washer.
First access the front sprocket, usually by removing a cover held in place by hex-headed bolts. It may be necessary to remove the gear lever before removing the cover.
If so, ensure the gearbox is in neutral and mark the gear lever clamp and splined shaft so it can be refitted in the same position.
The area behind the sprocket cover is likely to be extremely messy with old chain lube and road dirt, so have degreaser and rags on hand to clear up if necessary.
If the sprocket is held on by a single large nut, you’ll need to flatten its tab washer using a small chisel, punch or old flat-bladed screwdriver. The nut should be very tight (if not, consider yourself lucky on several counts) and can be awkward to undo given that the sprocket will rotate as you try to loosen the nut.
Ideally you should use an air-powered impact driver, but it’s possible (if not strictly best practice) to hold the rear wheel and chain in place by pressing hard on the rear brake and loosening the nut with a breaker bar.
This is best done with the bike on its sidestand and with someone to help, both to operate the rear brake and to hold the bike securely.
Alternatively, it’s possible to secure the wheel/chain by placing a block of wood or a cloth-wrapped metal bar across the swingarm and through the wheel to stop it turning.
Smaller-capacity machines’ front sprockets are often held on by a splined flange and two bolts. These are usually much easier to remove, but it might still be necessary to prevent the rear wheel from turning in order to undo the bolts.
If the old chain is worn enough to allow an easy swap of the old sprocket for new, then do so now. If not, loosen the rear wheel, slacken the chain right off and then replace the sprocket and tab washer if necessary.
Temporarily re-tension the chain and retighten the rear wheel, then tighten the sprocket nut/s to the correct torque, using the same method as before to stop the wheel turning. Doing this now avoids putting undue stress through the new chain later.
Put the motorcycle on its centre or paddock/workshop stand and remove the rear wheel. Set it flat down, sprocket side up but resting on an old tyre or blocks of wood to avoid damaging the disc or hub.
Undo the sprocket nuts, (sometimes secured by tab washers), and remove the old sprocket. Fit the new rear sprocket, and new tab washers if required, tighten the nuts to the correct torque and refit the rear wheel with the old chain loosely in place.
If the old chain uses a split link, remove the U-shaped retaining clip by knocking it forward from its open end with a flat-bladed screwdriver, then prise off the sideplate and remove the link itself. If the chain is endless or has a soft rivet link, you’ll need a chain-breaking tool.
In the case of a factory-fitted endless chain, it doesn’t matter which link you choose to break, but if it has a soft link, ideally find that and break it there. Refer to the chain breaking tool’s instructions and familiarise yourself with its operation.
Once broken, leave the upper run of the old chain hanging over the rear sprocket and temporarily attach its end to one end of the new chain using the new joining link.
Then pull the new chain into place around the sprockets, being careful not to let it drag on a dirty floor or through any built-up dirt around the swingarm pivot and front sprocket housing.
Assuming the supplied chain is of the correct length, attach its two ends together. Pack grease inside the exposed rollers at each end, fit a pair of O-rings to the joining link (if applicable) and, holding the two ends together around the rear sprocket, slide the joining link’s pins through the rollers.
Once in place, and again if applicable, fit the other pair of O-rings over the exposed ends of the pins.
Fit the joining link’s sideplate. If it’s a split-link chain, the sideplate is likely to fit over the pins relatively easily.
Once in position, with the circumferential grooves on each pin fully exposed, secure it by snapping the new spring clip into place with pliers. Make sure the closed end of the spring clip faces the direction of the chain’s travel.
A soft or rivet link’s sideplate is likely to be an interference fit, in which case you should use the chain tool’s press-fitting function (it is possible to ease the sideplate into place using self-locking pliers and some washers over the heads of the link pins, but this method runs the risk of warping the sideplate and/or pins and is best avoided).
With the sideplate fitted, the link pins’ heads need riveting in place, again using the chain tool according to its instructions.
Note that proper fitting of the joining link, whether of the split or rivet link type, is absolutely crucial – a poorly fitted link can easily break under load, causing damage to the machine and possible serious injury to the rider or pillion passenger.
Finally, refit the front sprocket cover and gear lever (using the mark made earlier to ensure the gear lever clamp is positioned correctly on the shaft), correctly adjust and tension the chain, retighten the rear wheel and lightly lubricate the chain. Job done.