When you get your first big bike, it can take some time to get used to all the mechanical noises that it makes, and they can seem quite worrying at first.
If you're on a tight budget and your new bike is a bit long in the tooth, there are a few noises that you should watch out for.
If your bike seems to be making a 'tinkling' sort of noise, especially on the overrun, chances are the camchain tensioner is getting loose and allowing the chain to rattle in its tunnel.
A constant rattling sound from the top end is indicative of loose valve clearances.
If it has started making a rattling noise in top gear, and it's been given a bit of a tune, it could be 'pinking'.
This happens when the fuel is exploding rather than burning in a controlled way. The rattle that you can hear when you're riding in top is the sound of the explosion in the cylinder.
What happens is that the pressure in the combustion chamber increases at such a speed that the fuel/air mixture farthest away from the plug is ignited by this pressure rise, instead of by the spark from the plug.
The usual causes of pinking are that the timing is too advanced so the spark is coming at the wrong time in the stroke, the compression ratio is too high, the fuel octane is too low, the fuel/air mixture is too weak, or the spark isn¹t strong enough.
The most likely factors are the plugs, or the mixture. Pinking is normally more noticeable when accelerating in a high gear as the mixture usually weakens off a little under those conditions.
The first step to getting a bike running properly is normally a new set of spark plugs and a jetting check. Sometimes it is worth using a fuel additive to raise the octane.
There are several brands on the market from bike shops or petrol stations.
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