"Hot" is a relative term though. Last week was extremely hot (in the UK) so when did you try it? A very hot engine is usually a weak mixture, wrong timing, "tight" engine, inefficient oil pump, valve timing out, leaking head gasket, tight tappets, binding brakes, soft tyres, etc etc or mixtures and parts of all of it.
If the carb is the same as when it ran OK before (you have had it running OK I take it?) then that can be discounted (provided the flange isn't badly leaking) but you need to check everything you've done.
Is it down on power too?