Nick Nomikos is the Sales and Service manager of The Two Wheel Centre in Harpenden. An MoT tester since 2002, he’s worked at the family-owned shop since it opened in 1991; “If drawing attention to the importance of basic bike maintenance encourages more people to keep an eye on their bikes, then we’ve won!”
What’s going on here? The customer came in on their Yamaha SR125 with a gearbox problem – they said it was jumping out of gear. When we went outside, we saw straight away that the chain was too loose, but on closer inspection, it was obvious that the sprocket was really badly worn, so there was nothing wrong with the gearbox at all.
Why does it matter? If the chain’s worn and gets loose it could come off, potentially locking the wheel or even wrapping itself around the rider’s leg. It might just unravel itself, but it could end up on the car – or biker – behind you. And when it comes off, the least it will do is make a mess of the chain adjusters, the sprocket nuts, swing-arm… the bill can get pretty steep pretty quickly! Anything on a bike that’s too loose is dangerous because of where it can go.
How do we stop this happening to us? It’s simply general bike maintenance – the customer really should have kept an eye on it; weekly if the bike’s being used a lot. Check the setting on the sticker, or in your owner’s manual – it’ll give a measurement below the swing-arm that your chain needs to be kept adjusted to.
Most bikes have a chain adjuster on either side of the swing-arm – assuming the wheel is in there straight when you start, turn each adjuster by exactly the same amount. If your bike has good markings on the side, ensure the pointer is in the same position on the left and right. Keep the wheel pushed in firmly as you adjust it and as you tighten the wheel back up to the correct torque, making sure you check the measurement again when you’ve finished – on some machines, the chain can go tighter when it’s all nipped up.
If you’ve reached the end of the adjustment on your chain, you must replace it. And always check for tight spots – if you adjust the chain to a loose area, it will go tight as the wheel turns.
Due to the position of the front and rear sprockets relative to the swing-arm pivot, no two bikes will necessarily need the chain adjusting to the same point – make sure you check. If you’re not sure, just pop in to your local dealer and ask for some help.
How do we fix this? Just replace it. The chain and two sprockets (front and rear) must always be replaced at the same time. And please don’t be tempted to flip the rear sprocket if yours is as bad as this!
Some small-capacity bikes have a split-link chain, which is easy to fit as it uses a simple catch to join it. However, it’s more likely you’ll need a tool to crush the rivets together when completing the loop after the chain has passed around the swing-arm pivot. You can also buy a continuous loop chain, but you’ll need to take the swing-arm out to fit this.
A lot of energy is transferred through the chain – if you’re in any doubt at all, book the bike in to your local dealer. Nick says he’d typically charge just £66 including VAT for the hour’s labour, with chain and sprockets costing anywhere between £30-£40 for a 125, to £150 to £200 for a sports bike.
Basic motorcycle maintenance is taught in the CBT, but a lot of riders forget about it. If you keep an eye on your bike, you can budget for any upcoming issues. As Nick says: “You should check your bike at least every month (really, before each journey). If you want to ride on a Sunday, check it on the Wednesday – put it on charge, check the tyres, chain, oil, coolant, brake fluid... If you don’t look over it, how can you be sure it hasn’t developed a leak? And keeping your bike clean is a great way to really know it inside out.”