G'Day Mike, sorry I took awhile to reply to your message, I'm working on an Air Force base about 150 miles from home with no internet access, so I only get to reply when I get back home on weekends.
Anyway, yeah, the F2/F3 heads are dodgy, don't get too morose though, although a little more fragile than the earlier K's and F's, they're also the fastest and best handlers, so well worth the additional maintenance, if and when it's required.
I've had two F2's, the first one was a high mileage "one owner" that was mechanically perfect due mainly to some loving maintenance by the PO, apart from some frustrating wet weather ignition problems which eventually were cured by the replacement of the ignition switch, it never missed a beat and had no problems with the F2/F3 "Achilles heel", the cylinder head.
My current F2 which I restored and rode about 50 miles before I couldn't live with the leaking engine cases (long story) any longer and parked it for when I get time to tear the engine down again, was an "Ebay Bargain", i.e., the biggest heap of shiite that God ever shovelled guts into. You name the problem, it had it, so I spent about a year buying, borrowing and begging the guys here for parts, and all I used from the original bike was the bare frame and wheels, and some engine parts, everything else was beyond repair, and yes, the head was stuffed too, all because the PO's were dumb shiites who shouldn't have been allowed to operate hand tools.
Re: your tappet noise, yeah, it sounds like a clearance problem alright, don't think you can fix it just by tightening them up though, a little noise is a lot better than no compression due to valves not being fully closed when hot. (and they all go tick tick tick) Oil pressure on our bikes should ideally be around 60 PSI, but when hot, I've often seen oil pressure guages hardly registering past 20 psi, so I don't use the recommended oil grades in warmer weather, I like a thicker oil that "clings" to the cam and cam bearings, (the items that are too often destroyed due to oil starvation due to heat/oil pressure issues) so I use Penrite HPR30 or HPR40, and my engines seem to run cooler, and definitely quieter.
I'd suggest strongly that you fit an oil pressure gauge to test your oil pressure Mike, (have a look on Ebay) and consider fitting an oil cooler. Yeah, I make and sell cooler kits for our bikes, but I'm not trying to sell you one, however, I'd recommend fitting one to any old bike, they're cheap insurance against horrific repair bills. Try some thicker oil, and adjust your valves to .002 thou (inlet) and .003 thou exhaust. Enjoy that bike mate, they are a little fragile, but they're quicker than any of the other SOHC4's, and a pleasure in the canyons! Cheers, Terry.