DON’T WAIT TILL YOUR CHAIN IS DRAGGING ON THE GROUND BEFORE REPLACING IT. CHECK YOUR SPROCKETS FOR WEAR REGULARLY AND EACH TIME YOU LUBE YOUR CHAIN AND CHECK THE TENSION, TEST IT IN SEVERAL PLACES. A SEVERE TIGHT SPOT WILL BE ANOTHER REASON THE SET NEEDS REPLACING. AFTER ALL, SHOULD THE CHAIN FAIL AND WHIP FORWARD, A CHAIN AND SPROCKETS ARE CHEAPER THAN NEW CRANKCASES.
STORY MAX SULLIVAN
Good-quality chain and sprockets are not cheap. Do yourself a favour and only replace worn components as a set — it will be cheaper in the long run.
PHOTOGRAPHY MAX SULLIVAN
TAP THE TAB
Remove the front sprocket cover to gain access to the sprocket nut. It will have a lock tab to keep it from working loose. Use a drift or punch to push the tab back so a socket can be used to loosen the nut. Some lock tabs have one or two tabs. This one is circular and can be reused a number of times as long as the previous part is not re-bent, as this will cause a weak spot and the tab will fail. If no unused tabs are left on the lock tab, a new one is in order.
After you’ve loosened the front sprocket nut, it’s time to remove the old chain. Don’t remove the chain first as it’s then difficult to hold the front sprocket while you loosen the nut. If no clip link is evident, use an angle grinder or specific chain breaker to cut the chain. A good-quality chain breaker will push a pin straight out and allow the chain to be removed. If you only have an angle grinder, grind the end off two pins on the same link and tap off the end plate.
Take out the rear wheel to access the rear sprocket. The rear sprocket might be bolted directly to the rear hub or, as in this case, bolted to the sprocket carrier. A cush drive like this is used for bigger touring-type dirtbikes as well as in desert racing to reduce the shock load to the gearbox. The sprocket carrier will just lift out but you’ll find a spacer inside which is mounted between the sprocket carrier and rear wheel bearing. Do not lose this spacer or a seized wheel will result!
Replace the rear wheel back into the swingarm and move the chain adjusters all the way forward. Push the rear wheel as far forward as possible then feed the chain around the swingarm and front sprocket. Take note of any chain sliders or rollers that might be fitted. Wrap the chain around the rear sprocket and line up two “inner” links ready to make the cut. You need to have two inner links butted together so the joining link can slide through both of the pinholes. Use the chain breaker or grinder to shorten the chain to the correct length.
Be careful loosening the rear sprocket bolts if you’re not working on a cush drive hub — it’s very easy to slip and take some skin off your knuckles on the sharp, worn-out sprocket. If you have the luxury of a cush drive, mount the old sprocket in a workshop vice and you can loosen the mounting bolts with relative safety. You can see the hooking of the teeth on this sprocket, indicating it’s overdue for replacement.
Before fitting the new rear sprocket, check the mating surface is clean and free from dirt or corrosion. Inspect the bolt holes in the hub for cracks or any wear. If foreign material is caught between the new sprocket and the hub, it may dislodge as you ride, causing the sprocket to come slightly loose. If the new sprocket is painted, it’s a good idea to remove the paint from the mating surface for the same reasons. A loose sprocket can then lead to worn or broken hubs and a big repair bill.
Fit the new sprocket onto the hub or, in this case, sprocket carrier. Dab a little threadlock onto the sprocket bolts to ensure they stay tight. If any of the sprocket bolts look damaged in any way, replace them; if the bolts break or come loose, this will cause severe damage to the rear hub or sprocket carrier. If the sprocket bolts have allen heads on them, use an allen key to hold the bolt and tension the nut with a socket. Do not try to tighten the bolt as the correct tension will not be reached.
Before you refit the rear wheel, check the wheel bearings and seals for damage. Now is also a great time to completely remove the chain adjuster bolts. Because these bolts go right through the end of the swingarm, the internal, exposed end is subject to moisture and can corrode. Either the bolt may corrode in the swingarm thread or the corrosion on the bolt thread will destroy the swingarm thread as the bolt is turned. Coat the bolt thread with anti-seize and refit the bolt to the swingarm.
If your chain comes with a clip-style link, make sure the “nose” of the clip is fitted in the direction of rotation. In this case we’re fitting a rivet link, so double-check the chain length before fitting. If the chain is too long, you’ll need to purchase another rivet link, since they cannot be reused. Make sure the O rings are fitted to the joining link, then press on the outer plate. It has to be on far enough to rivet the end of the pins, but not so far as to restrict movement in the link. A special rivet end is fitted to the tool to flare the end of the link pin.
Adjust the drive chain tension to the manufacturer’s specifications and tighten the rear axle. Check the chain for any tight spots or unusual noises which might indicate a problem. When adjusting the chain tension, lean toward the tighter side of the specs as the new chain will settle in and become loose in a short period of time. With a new or suitable lock tab fitted, tension the front sprocket and fold over the lock tab to ensure it stays tight. A little liquid threadlock is a good idea to assist the lock tab. Now hit the trails with confidence!