First, if there are three rings, it is usual to fit the ring gaps at 120 degree angles to each other. I was taught long ago to fit each ring at 180 degrees to the one above it - in those days there were often 4 rings, sometimes more, so even spacing wasn't going to cut it. Usually, I tend to just do what the workshop manual says, which in this case is 120 degrees.

The folded mesh screen in the PCV compartment stands on edge in the deep vertical slot in the bottom of the compartment. You want it to get in the way of pressure waves passing into the breather tube, because the role of the screen is to filter out tiny droplets of liquid oil: you want the droplets to trickle down through the mesh, then run down the slope at the bottom of the slot, to the drain-hole at the opposite end of that slot from the port leading to the breather tube. There is a baffle in the compartment, so you can leave a space between the end of the mesh and the breather port. If you don't do that, the section of mesh positioned up against the port could get crudded up and obstruct the port. See this picture:
[Linked Image]

Honda's design of that compartment, as of most things, is rather well thought-out. And the picture is of a scrap GXV120 block - there isn't much point in cleaning scrap, in my opinion anyway.

Remember to push a 1/16" drill bit downward through that drain-hole, then pull it back out:

[Linked Image]

The picture is taken from inside the crankcase, of course. The red circle is around the drain hole.

The tiny drain-hole sometimes becomes obstructed by a build-up of crud over the years, and that is a problem because it results in the compartment gradually filling with oil, which then goes through the breather tube into the engine intake. So, just hold the drill bit in your fingers, push it deeply through the drain hole, then pull it back out. This is done from the PCV compartment - you don't need to do it from inside the crankcase.