Look for a split seam or split flange on the fuel line from the tank to the pump, and from the pump to the carb. Also check for air leaking around the inlet fitting on your clear filter. Also pressure test your filter by capping off the outlet and applying 6 psi to the inlet and see if it leaks through the body or seams (use a bicycle pump with a pool toy nozzle). For you to have air in the filter, you either have a leak on the suction side of the pump (most likely) or on the pressure side, but you should be able to see or smell a leak on the pressure side. You should not smell fuel at any time. I don't like rubber fuel line over the engine; I use steel from the pump to the carb. Rubber eventually dries out and cracks, is susceptible to burning, and clamps can leak.

If you can't find a leak anywhere, try changing brands of gas. Look for non-oxygenated fuel. Ask the station owners who supplies the fuel and look on the fuel supplier's website. This should not be a heat related problem unless your fuel line lies directly on your intake manifold or block, in which case it is a routing problem.