My Thorn has had an annoying click for the last couple of months... I removed the cranks, slid out the EBB, reassembled it; did an oil change; fitted new pedals (which were on their last legs)... and still this infernal clicking, every 2 or 3 pedal strokes. It seemed to be coming from the rear sprocket, but I realised that if the chain had a stiff link in it, that could make a click every time it went round the sprocket. Lo and behold I found the stiff link.... which looked like this...
The stiff link (in the centre of the photo) has a broken roller... which may be the cause of the stiffness. I've never had a broken chain before... how exciting! I'll remove that link from the chain and revert my EBB back to the "as new" position.