Suspected Cam/Timing chain chatter

[His Dudeness]

I've had a dodgy starter clutch before. I think they go bad from starting the bike with a weak battery too often. Most of the time it was fine, there was no noise from it, then when it acted up it'd give off a deep rumble in time with the engine rpm however on mine if you turned the engine off and turned it back on it'd go back to normal with no noise. Also there was no metal in the oil. Yours sounds a bit worse than that but hopefully the starter clutch is your problem because it'd be a cheap fix. If I was you I'd try the trick with rotating the piston to bdc and push down on it with a screwdriver and feel for movement.