Engine/Gearbox Noise?

[nato]

So I blew the dust of my 12 300 and went to go for a ride and im having a knocking noise when under load. I threw it on the stand put it in gear and gently eased the brake on until started to knock and it sounds to me as though it is coming from behind the clutch. Any ideas on where to start looking? Its not the bash plate or pipe spigot type noise but a definite clunk in speed with the drive of the box.

[5valve]

In my case, loosened clutch basket nut, not torqued as per updated value.

[Brian VT]

Chain slap on the swingarm slider ?

[Zman]

I get that noise when my chain is worn out and loose.

[nato]

Hmm the chain is knackered but sounds transmission related. Worth a look though.

[nato]

So I took the chain route today and replaced it and sprockets. Noise appears to be gone. 3000km pn the stock chain is clearly enough thanks guys for the advice.

Nato