That’s where if you can depending on what bike you have 

thanks perthhog for some reason after checking out tensioner & compensator & a general look round I put back together fresh oil & it seems a lot better just faint whirring at 30kph ( off throttle) can`t hear anything while cruising at 30kph thou hmmm

Inner primary, correct @$40.00 as you can see the wear grooves. Noise seemed to appear over night,I always think the worst when shit go's wrong.

When you get your primary off, just check and see if you have any play in the clutch hub.  I had a similar noise and mine turned out to be a clutch bearing which I replaced last Satdee.

If you messed about with the tensioner and it got better, it good be your primary chain was too tight. Does yours have an auto tensioner? these often make the chain too tight.  

Ok something to consider thanks Lushy. mine has auto tensioner,I just compressed it with Zip tie and removed to check for grooves,was pretty good then put it back on , & the chain did have bout tad over 1/2" free play at top but after riding down to Moruya Panhead show & back 260k round trip can still hear it whirring no louder thou (for now) but will need it looked at cheers 

Im sure The clutch hub bearing doesn't spin until you pull the clutch in. So if the noise is only there when the clutch is pulled in then that would more and likely be the buggered one.