Suburban SW6 lights but drops out after 30+ seconds

I have a feeling these last two posts may be the issue then.
a) I scrapped the tube where the gas burins, lightly with a brush and blew out with air nossle. Lots of **** came out. I did not do anything to the little orface at the begging of the round gas tube so if I clean the round burner tube where the flame is, will that help ?
b) It appears to vent out the front and that is clear. I will look into burner tube to see how that looks at the back.