For the longest time I had problems with Robert Shaw pilot burners. The suckers fairly often just wouldn't clean up. Sometimes putting in a new pilot orifice worked, and sometimes it didn't.
Getting advice on this forum helped solve the problem for me, and I want to repost what I've learned.
The main problem is that it can be tougher to clean these pilot burners than any others, in my experience. Take a Robert Shaw pilotm burner in your hand, remove the pilot orifice and look up into the main part of the pilot burner. you will see an internal cylinder supported by brackets.
I think that internal cylinder helps create an aerated pilot, with air being sucked down the outside, mixing with the fuel gas from the orifice and then mixing and going up the inner cylinder.
Aerated pilots tend to collect dust and junk and become plugged, and getting that inner and outer cylinder plugged with that junk is the key to a well functioning Robert Shaw pilot.
The thorough way to clean it is to take out the pilot orifice and use a pipe cleaner from the bottom to clean out the accumulated gunk. That's a job, but solves the problem every time in my experience. You can add a new pilot orifice for peak performance.
The cheap and easy way is to use canned air to spray into the top of the pilot burner without removing the pilot orifice. This produces a reasonable pilot flame much of the time. Buy canned air with a long, think plastic tube that allows you to direct the air flow right into the pilot burner.
The Robert Shaw Pilot orifice has a square hole which can't be cleaned effectively with a drill bit or bristle from a wire brush. I'll often try blowing them out to clean them, but if that still produces a poor flame, I carry new ones and replace it.