Insulate the fuel line where its closest to a heat source might help. My 250 had a fuel line the went around the front of the motor between the thermostat housing and valve cover, I always had restart issues if I didn't wait long enough for the fuel to dry out. I suspect it was caused just by what Jon mentioned above. I have since rerouted the line straight up out of the pump and over the valve cover right into the carbs, eliminating quite a bit of line and avoiding the heat of the thermostat housing. Starting issues are way better now, and with a lot less fuel odor.
