The K0/K1 "large" oil jets can get very stuck in their holes. When that happens, it might actually be best to leave them there, as removing them forcibly can damage them - and they are rarer than rocking horse poop...
I've successfully used MAPP gas torch heat around them on the head itself, then tapped them out from below while hot (yes, burned my fingers, too). If you damage the domed filter on the bottom side, here is the stuff to know about the design:
1. The holes in the mesh are 0.002" smaller than the hole that the oil comes out of on the top, this is the "strainer" function.
2. There are 13 holes in the domed mesh, while the other few around the perimeter don't flow any oil because they are crimped against the outer ring of the oil jet body. You only need 3 of them to be open in order for it to work, and the post-K1 style oil jets (the little ones) have just 7 holes total, all the same size as these. The metering hole in the later jets is the same size until the F2/3 and K7/8 engines, then it got 0.002" bigger.
3. The later engines (not the early ones) will actually run just fine with their oil jets REMOVED. I know this from working on an engine that ran from Michigan to California, then was sent to me for general overhaul (mostly cosmetic) for a show bike, and inside it was perfect, except for missing the oil jets completely.
4. If you end up denting the strainer dome in the attempts to remove it, just make sure it is still mechanically sealed (crimped) around its edges when you put it back in, and it will work just fine.
If they are hopelessly stuck, I just warn the machine shop to watch out for them when they wash the head for me. In all that I have done (it has to be more than 150 of the early heads by now), only one popped a big jet out during the washing, and they found it inside the parts strainer afterward.
