What's that noise? Motorbike troubleshooting by sound
Bike engines will make a variety of noises; hardly surprising with several hundred metal parts whizzing round thousands of time a minute.
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If you are worried about the mechanical noises coming from your bike, then it’s well worth investing in a workshop stethoscope.
They aren’t the doctor–type with flexible tubes, but use a stick to let you delve into the middle of the engine. They only cost about £10-20.
Diagnosis by noise: the sounds your motorbike makes
Start out by listening at different points around the engine, like the cylinder head valve caps, or the camchain tensioner mechanism.
An engine will often sound noisy on start-up because components aren’t under load, the engine is cold and the oil hasn’t warmed up and started circulating freely. But then it should settle down to a regular beat.
If a noise persists, or increases in volume, then that could indicate excessive wear.
Nine motorbike noises that mean you should take action
- Sudden ticking
- Variable ticking
- Clattering and slapping
- Drive chain din
- In-gear whining
- Braking knock
Does your motor sound like Homer Simpson’s guts after a night on the Duff? Time for a look at your cooling system. Coolant should circulate silently. Firstly, check the level, any drop indicates an issue. If there’s an air pocket, the pump won’t be able to circulate coolant properly, and it can froth around and boil if it can’t circulate away from hot spots. Top it up – if it drops again you may have a leaking seal or gasket. Bubbling coolant, or coolant being forced into the header tank too readily, may indicate a blown head gasket or another overheating problem that needs investigation.
Does it sound like there’s a bag of stopwatches under the tank? Start at the exhaust headers, especially if they’re old, or have recently been fitted/disturbed. A small gap in the manifold seal, a loose header collar or a small hole opening up in rusty pipes can result in a ticking sound. It’s best checked when cold – you might see a bit of steam issuing or water dribbling out in the first few seconds, and you can hold a hand close to feel for escaping gas without getting burnt.
If your exhaust is nice and sealed, and you’ve got a tick that drops off as the bike warms but rises with revs, check when your valve clearances were last inspected, and if they’re due have them looked at. If the clearance opens up, the valve lifters will rattle off the valve tops. It’s not immediately catastrophic, but very loose valves cost performance, and will eventually put too much strain on the top end. A stethoscope can help you narrow noises down to a certain area.
If you’ve got a clattering that’s most prevalent at tickover, or off the throttle, your camchain (or tensioner) might be at the end of its days. Just like a drive chain, they stretch and reach a wear limit that the tensioner can’t compensate for, or some bikes can suffer with camchain tensioners fatiguing. Either way, the chain can flap and cause noise. It’s in danger of skipping a tooth – at best, performance suffers . It’s often worse – valve timing goes out, and valves/pistons can meet.
Got a whirring, high-frequency metallic noise that doesn’t seem related to engine speed? Look to your drive chain. A healthy chain is noisy anyway, but you shouldn’t be able to hear it yourself while you’re riding along. A vibration or clanking (sometimes felt though footpegs too) signifies tight spots or stiff links. You should thoroughly clean your chain and inspect for stuck links, loose rollers and excess stretch. If that’s all OK, make sure it’s properly aligned and adjusted. Lubricate with decent lube on the inside run first, preferably when the chain is warm. If you find any tight spots, stiff links or have run out of adjustment then the time has come to ditch the chain and invest in a fresher (quieter) new one.
A solid-sounding knocking emanating from deep in the motor is very bad news and is usually related to the engine’s bottom end — the crankshaft and conrods. Worn big-end shells and collapsed bearings can and will seize your engine if they expire as you’re riding along. As soon as you hear anything metallically clunky coming from the motor, hit the kill switch, come to a safe stop, and prepare for serious investigation. And probably a serious repair bill. Don’t try and clear it by revving it harder, it won’t magically improve things, it’s definitely not that sort of problem. Unless you are a competent spannerman, this is one for your local dealer.
Some bikes crackle a bit on the overrun, but big bangs and constant popping isn’t normal. Check the exhaust joins for gaps – leaking gas, if it’s not immediately obvious, is often betrayed by little carbon deposits, or condensation dripping as it warms up. In any case, some expert dyno time can help get to the root of improper running.
Whining under load usually signifies a gearbox issue. If it’s only doing it in one or two gears, it’s probably isolated wear – gears work in pairs and a problem in one gear often makes itself known in another. If it whines through every ratio, suspect a gearbox bearing is worn and causing the shafts to run out of alignment.
Noise when braking? There are three possibilities: your calipers have an anti-rattle plate and if it’s incorrectly fitted the pads can move around. If all is OK there, lift the front end off the floor and feel for play in the head bearings; a small amount of movement is enough to make a noise. Finally, check your forks – worn internals can result in a knocking noise too.