Platwound here are some pictures of a Birdview gear drive set up an how to take some play out of it's 2 gears how they mess together, if you need to do it, but remember that some play is needed. now on 1 of my mounts here it had so much play in it you could move the edge of the dish about a 1 1/2" or more, after I tighten it up when reinstalling it now only about 1/4" at the edge of the dish.
now you need to have it all dismantled, before trying any thing like this. remove the gear drive 1/2 moon an (7 5/16" carriage bolts) worm bracket from it's plate that bolts to the reflector, this has to remove due to lining it back up with the bushing in that plate. an mark it before taking it apart. after removing the 1/2 moon gear (just slides out no need to remove the worm), this needs to be done with a clean gear an worm no grease on it clean, only need to move the cam 1, 2, or 3 teeth from you're mark, an then check you're play. you may of made more play if so go in the other direction.
now if you think that you got it set perfect, test run it by hand an see if their is any binding or exsive slope from 1 end of the ark to the other. I do this with a socket that has a notch cut in it an a battery drill with the clutch set very light in the drill just enough to run the worm with out it slipping.
1st picture is of the gear drive removed from it's mounting plate, an marked a line for reverence.
2nd picture (not the best pict) small side of cam.
3rd picture measurement of large side of cam
4th picture lokking down at the cam, if you look at closely you can see that it is not round but a cam for adding or removing play in the gears.