Had this fitted to a 400/4 camshaft I bought off ebay some weeks back - the cam is fine, the sprocket is a little worse for wear...
Needless to say the chain has been jumping the teeth to a large extent! On say a rear drivechain sprocket this is easily do-able by the mechanically unsympathetic - surely on a cam sprocket it would only jump a few before mechanical carnage ensued between pistons & valves, stopping the engine?
My only guess is that the owner had run a presumably very noisy loose camchain for quite a while, running the sprocket teeth into needlepoints before it finally slipped round, taking the tops off?
Your thoughts: