...pistons and rings new. Cylinders brushed with 150 grit as mentioned.
What do you mean with finish problems? Bad honing? Possible; yes.
When you hone a cylinder with such coarse stones what do you expect the outcome to be?
Honing a cylinder, particularly with coarse stones, leaves peaks and valleys on the cylinder wall. The piston rings ride on the peaks, although the break in process knocks those peaks down to a point. The oil control ring scrapes the majority of the oil off the cylinder walls but it cannot scrape the oil out of the valleys. This is fine because the rings still need some lube. The oil in those valleys is ultimately burned, and when enough oil is in those valleys and burned it will manifest itself as smoke and oil smell. You could replace the oil control ring repeatedly and still have the same results if the cylinder wall finish never changes.
One of the other things I deal with on a daily basis are aircraft engines. It used to be common to repair cylinders by chrome plating them, which would leave a hard, crackled looking finish. Soft iron rings are used in these cylinders so there aren’t break in concerns yet they are notorious for burning a lot of oil. The answer is the same as what I wrote above, the oil consumption will never stop until the cylinders are thrown away and replaced with something that has a different bore preparation.
I’m aware that many recommend using iron rings and coarse stones on Triumph cylinders. That said, I don’t think I’ve seen anyone recommend something as coarse as 150 grit. The installation instructions that came with my MAP pistons and rings is more in line with what I would expect, which from what I remember is 240 grit and a 600 grit finish.
All this assumes that you have proper clearances on all the components and that you have straight bores as well.
