There is little mystery in this story. Once fuel is in a hot float bowl at atmospheric pressure, if fuel temperature exceeds the boiling point of the lightest fraction (usually Butane in winter mogas), bubbles result, those bubbles are pulled into into the main jet and you have a very lean mixture.
Winter mogas has about double the vapor pressure of summer mogas. This is a good reason to be careful using winter mogas on a warm day or at higher altitudes where pressure and therefore boiling point is lower.
Like I said, some winter gasolines will start to boil at just over 100F at sea level. That's easily exceeded on a heat soaked engine with carbs. Be aware that gasoline formulations are molded around the fact that most cars have been fuel injected for a couple of decades and EFI picks up cold fuel in the tank and pressurizes it before it reaches the engine. This drastically reduces the chances of vapor lock issues compared to carbs.
All this being said, mogas was not designed for aviation use. It may work fine if you're careful. Here is a good graphical representation of the vapor pressure variances in mogas vs. avgas: http://www.bp.com/content/dam/bp-air...%20leaflet.pdf
Personally, it would give me the willies to run a carbed engine on winter mogas. I run it in my Subaru but it has EFI and I use up the winter mogas before it gets warmer. I've drained it out of the -6 and put it in my car on occasion because it wasn't safe IMO. I bought a Peterson tester when I switched from 100LL to mogas and that was pretty eye opening. There's a big difference between the 2 fuels.