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What is motorcycle idle ?

If you are an experienced motorcycle rider, you probably know the term "Idle" perfectly well, but we do get the "What is idle" question quite frequently, so it's not common knowledge for everyone.

This is what idle is all about.


Idle is the engine condition where the engine is running but you are not touching the throttle grip. So your motorcycle engine is running at idle speed when you start it up in the morning (Until you start riding the bike), or when you are stopping at a red light and the engine is kept running.

The correct motorcycle idle speed depends on the engine layout and the air/fuel mixture, and the correct idle speed is decided by the manufactorer (And you can see the correct idle speed for your motorcycle in the owners manual)

The idle speed that is determined by the manufactorer depends on a number of factors.


On one hand, the manufactorer wants to set the motorcycle idle speed as low as possible for these reasons:

- Less noise
- Lower fuel consumption
- Less "Clunk" from the gearbox when you enter first gear


But the following factors are limiting how low they can set the idle speed:

- Engine will stall if they set the idle speed too low (Either at idle, take off, or when you close the throttle to slow down)
- Oil pressure will be very low at low RPM's and they must ensure that the engine internals are sufficiently lubricated at all times.

On older (carburettor) motorcycles and the first generation of fuel injected bikes, the idle level is controlled by a simple adjustable "Stop Screw" that prevents the throttle valves from closing fully, so on these bikes it is relatively easy to set the desired idle level.

On modern motorcycles, the idle level is controlled by one of the bikes computers, and it is mostly not possible to adjust the idle.

It is also important to understand that if your idle level is suddenly too low or too high, it could mean that something is wrong with your bike that you need to get fixed first - just adjusting the idle level is not curing the core problem in this case.

There is a lot of additional information about the most common causes of idle problems on the next pages.