First, the Carb filter: You were right......it took a big 1" wrench to loosen the nut where the secondary fuel filter is located. There is a little "barrel" filter right at the inlet, which is held in place by a spring. Beyond this filter is a brass or stainless screen about an inch deep inside, and I think removal is done by taking the carb apart. However, I shined a light in, and it was not clogged. I used a few Qtips dipped in gas to lightly clean the screen, and no particles came off, only a bit of grime.
As you can see in the pics, the barrel filter did have some black sludge laying in the bottom of the filter. Amazing that all this crud gets past the larger filter that is a foot from the carb. When gas is pumping up and through this barrel filter, it would mix with the gas, and could possibly restrict the gas flow going into the carb. So, I cleaned it all out in gas, and put it back.
In the pictures, you might also notice the "wet gleam" all over the intake manifold......appears that there has been excess gas leaking here. Possibly a carb float not closing properly?
The last pic shows a pic of the oil dipstick......oil was changed 3/2018, and only has 750 miles on it. It is right at the Full mark (a wee bit above), and "seems" to have a very slight gas smell. Also a bit on the thin side, but I did add a quart of Marvel Mystery Oil during the last oil change.
