If both these sounds started at the same time, they might be related, and over fuelling is a possibility that comes to mind, which just might result in your brick running on only three cylinders, that can cause a knock.
Removing the return hose from the tank and directing it temporarily into a bucket, just might improve the problem, tending to confirm this guess. Directing a spark plug lead to a spare, earthed, spark plug, should result in a drop in revs. If it doesn't result in a rev drop for one of the cylinders, that's a problem.
