Forget fuel vapourisation, shouldn't be a problem. The "traces of red" may well be old sealant, which should not never nohow need to be used here. You need the float needle to seal and the float at the right height. Condensor problems do show up on a hot machine being restarted because of lower cranking speed and heat soaking into the offending instrument causing a condition known in the trade as D.O.Z.* The manifold should not be damn hot, by the way. Any possibility of a bowed flange on the stub or a leak of air? Cheers, F5AB/2A/7945 since 1970. *(Devoid of Zaps)