Is there any metal on the oil screen or the magnet?
It sounds like the valve clearances are too large. If that's the case, the cam follower bearings (CFB's = rocker arm bearings) are suspect.
If you find either intake or exhaust clearances way too big, the valve cover needs to come off to check the CFB's.
When you pull the inspection caps, find TDC and wiggle the rockers up and down. Note how much if any movement there is, then kick the engine over 6-8 times or use the starter to turn it over.
Then find TDC again and do the wiggle test again. If it's different, even a tiny bit tighter or looser than before, the bearings are likely toast.