Hello, first post here. Last week I picked up a 1980 cb750. Just got it running and it has a knocking sound at idle that goes away with any revs at all. I was thinking cam chain but then by advice on a fourm I put it in gear (on the centre stand) then I put the brakes on and released the clutch about half way and it seems to go away. No metal in the oil thankfully, but I still really dont like the sound. Its hard to tell where the sound is coming from exactly there's lots of sound in my small garage and lots of intake noise with he airbag still not being on. Any ideas on how to rectify this?