the reason why tappets get ticky, is because the oil entering them, has to go thru a tiny hole(1-2mm diamter). if the oil dusnt get changed regulalry, then this hole getsa gummed up with crudd, as does the plunger inside. its the build up of oil pressure inside the tappet, that stops it from ticking. to get out the tappets, uv gota remove the camshafts, which onvolves removing the cambelt.
once the tappets r out, stick them in a jar of white spirit, pumping the plunger up and down, to expel all the oil black oil. keep doing this til the plunger moves freely under its own weight. from there, insert the tappet in a jar of clean oil, and work the plunger once again. this primes the tappet with new oil. place the tappet back into its bore(the correct way around), and repeat for all 16 tappets. that should keep the tappets nice n quiet for another 50-60k miles-unless of course they r worn to excess around the outside, or the plunger is buggered.
jimbo