Whirring sound

[bearvalley]

My transalp xl600 makes a whirring sound in third gear when decelerating.
any reason to be worried?AF

[StumpyFingers]

I would check the chain tension.
If that is not it, then it maybe the gearbox failing.

[pdsquire]

Or the chain-wear. It might actually do it in all gears but the combination of chain speed and lack of wind-noise means you only notice it in third.

If it IS unique to third then it can only be something inside the gearbox but they're rattly old things and only someone criminally-insane wants to take a gearbox apart until they have to.

I know it's a stupid question, but have you had it long? It might always have made that noise.

[bearvalley]

Ive had the bike since 2006 ,it only makes this sound in third gear when decelerating, but apart from the sound it seems to be smooth enough.
The chain tension is fine.its been making this sound since i got it 18000 miles its now done 24000.Could it be any plastic parts in the gearbox as i once owned a 400 n super dream which had plastic parts in the cam chain assembly.AF