If you are getting air in the primary- ie the first small usually opaque filter, you might have air coming in from somewhere between the tank and the filter, or the tank screen may be really clogged. A small bubble is not a major problem. Have you changed the secondary fuel filter lately? Is the primary fairly clean? Did you put a bit of fuel on the rubber of the secondary when you tightened it? I'm hinting at other than air problems because there are other causes that seem more likely than a "air bubble" which would cause loss of power. How often does the problem occur?