How to diagnose a problem by the noises your bike makes

By MCN -

Parts & accessories

 15 November 2010 15:27

Q. I’ve just started out on bikes and have a 10-year-old Suzuki Bandit 600 which is great fun.

But having come from cars with all that noise deadening bodywork and in-car entertainment to muffle the sound of the engine, I’m worried that my bike’s engine may have a problem, judging by the amount of mechanical noise it makes.

I’m sure most of it is just normal, but how do I tell the difference between the good and the bad?
 
A.
Bike engines will make a variety of noises, hardly surprising with several hundred metal parts whizzing round thousands of time a minute.

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 £20.

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.

Rumbling sounds are normally bearings in the bottom of the engine, perhaps the crankshaft. A “squawking” sound is probably the clutch wearing, while a metallic rattle that follows you shutting the throttle on a four-stroke means the camchain tensioner is worn.

A ticking sound from the top of the motor indicates that the tappets are worn or maybe the shims, depending on their design. An erratic idle or a sense that the engine is ‘hunting’ could indicate a duff plug or the carbs or injectors are out of sync.

If there’s a whining noise coming from the bottom end of the engine that means a gearbox bearing is knackered.

Finally, if your bike backfires or makes a ‘spitting’ sound, then there’s an air leak around the exhaust headers or further down the exhaust system.