FLSTC won't start when hot

[Fire Chief 74]

My 03 (carb) FLSTC after running it for more than 30 minutes and shutting it off sometimes won't start. It turns over just fine and will pop and backfire just won't start. If I pull the enrichment handle it does start. When it happens the bike is hot and so is the weather. This only happens sometimes. Most of the time it starts right up and runs good.
Any ideas?

 

[Stoney61]

Possible vapor lock? Next time it does that, loosen the gas cap and see if it starts then.