I've got a mystery sound on the bike. It started making a "clock" sound when I let out the clutch. A couple of days later I started getting a faint second "clock" as I mildly accelerated. Now I'm up to about 4 or 5 solid "clock" sounds. The pace of these is about the same rate as front tyre rotation. I doesn't sound slow enogh to be an entire rotation of the chain and I get the first one as soon as I let out the clutch. It doesn't get worse with speed. Steering head bearings? It's hard to check these without a centre stand, but I hadn't noticed any notchyness. Cam chain? I suppose I can check this by slacking off the manual tensioner a bit and seen if it gets worse. Any other thoughts?