Hi, from digest mode:

  A good tool to get the dust cap off  is one of those little dandelion
tools from your garden department.  I have about 3 of them kicking around in
all my tool boxes.  They look like a large bent screwdriver with a splayed
out head and a notch in it.  The notch is sharpened, I guess, for cutting
the stem of the weed below the surface of the ground and the ones I have are
kinda rounded elsewhere.  I suppose so that you only cut the stem you are
aiming for.  You may have to try a few garden supply departments until you
find one that is shaped just right.  Some are sharply pointed on the
outside, which might damage the dust cap or require you to take a grinding
wheel to it.
  Anyhow, the bent shaft is just right to allow you to 'pry' without hitting
the wheel edge or the tire with your knuckles. The flattened head /with the
centered V for cutting gives you two contact points under the cap's lip.  I
go round and round the cap, prying up at about 180degrees, then rotate the
wheel and pry again.
  Don Hanson