cheers for recording that did you do it on your phone? I will add it to the wiki when its back up and running. Thats what we want more of folks dodgy engine noises!!! as for your problem. yes there will be some oil that will come from the rocker covers, but not like loads, maybe an egg cup full, but that goes a long way. I've set the tappets on a bay but not one of these, I guess its similar. are you familiar with the workings of the flat 4 four? I recommend John Muirs
"idiot book" as a good primer for engine mechanics generally and especially air cooled flat fours. Also
http://auto.howstuffworks.com/camshaft.htm Anyway, working logically there is a metalic sound from your tappets, there are several bits to the valve train cam shaft (driven by the crank) cam followers, push rods rocker arms, valves, and keeping this all under tension are the valve springs. So as the cam shaft rotates the cam lobes lift the cam followers, which transfer that to the push rods which press against the rocker arm which opens the valve.
EDITED- the adjustment screw should be on the valve side not the pushrod side
In the case of solid lifters
the trick is that this system needs to have a bit of slack between the push rod and where it pushes against the rocker as when the engine warms up things expand and, hey presto! your drive train is now slightly longer and preventing your valve from closing fully. With a valve not fully closed your compression chamber will not seal so you are losing ooommmpppff! Also the exhaust valve transfers its nasty heat to the cylinder head in the brief moment it has in contact whith it. Bottom line is your valve should open and close fully too, too much tightness will lead to your valves not closing fully and overheating .
In the case of hydraulic lifters
these clever buggers use the oil in your engine to take the slack out of the system (hydraulic from hydro=water?) anyway the principle is that fluids cannot be compressed so you dont need the slack in the system that you do with solid lifters. HOWEVER when the engine is left unused for a while one or more of the lifters may drain down of there oil leaving air in the system under normal operation running the engine for a while bleed the air out and your all good again.
BUT you've still got that clackety clack after you have run the engine for 10 miles or so, so whats up? well maybe you have solid lifters put in when your engine was rebuilt, solid lifters are easier to set initially and CHEAPER. Because of this some engine reconditioners use these instead. In which case you've got to do the solid lifter adjustment. OR maybe those lifters/cam/engine is worn and not self adjusting correctly OR the valve is 'sticky' gunked up with thousands of miles of motoring the spring is not returning the valve to its seat, big gap causing rattle? any more offers?