String Trimmers

I have a 223L Trimmer with a hard to trace leak.  I had noticed residue under the engine in my shed and around the throttle assembly.  I filled a inspected...no leaking.  I set it up on some saw horses a waited one evening...nothing.  The next afternoon I returned from work to find residue on the concrete directly below the throttle assembly.  So now I'm suspecting extreme heat to be forcing gas out some where. We live in Southern Louisiana.  It is very hot.  I imagine my shed could get well over 100F.  It this a possibility? If so what should I do?