[redwing52]

If you use a car/truck experiences these bikes can confound you. I have to remind myself at times there are some unique issues that would not be common to a car. The fact that the tank is right over the hot engine and not in the cool back of a car. The same can apply to fuel lines. The carbs are somewhat protected by the foam rubber baffle deal but still I have percolation on very hot days. With all that said my opinion is that more likely the fuel had a chance to cool while you were wrenching and in fact that is why its started. Some air in fuel filters and fuel lines that run high in the vehicle is probably normal in any loop that is higher than the carb inlet especially if the hoses other end is below the inlet at any point. Sort of the same as the banjo fitting on the 1200's brake system but air in a fuel system is not an issue.
The buzzing that was mentioned is normal and there are threads that talk about it also. It is the fuel cap venting excess tank pressure from the hot expanded gas.

 

[redwing52]

Normally I would agree with Captain Midnight. No way, but if you think about it more??? In the new cars with the pump in the tank. (like the 1500's right?) In cars it just doesn't happen. The entire fuel line is under 20 or 30 PSI fuel pressure and the boiling point (vapor point) is too high for even the hottest weather.

The bike has several things working against it. First the tank is right over the engine so it gets lots of heat. Cars are nice and cool in the back.

Instead of 20 or 30 PSI fuel pressure like a car (that really raises the boiling point) the wing has only a little pressure.
Cars have most of the fuel line routed away from heat and then stainless line where heat is under the hood. The 1500 has most of the fuel lines exposed to engine heat as well as the carbs. (and tank as I said earlier) So given the hot day, sitting in stalled traffic, all the issues I listed above, I certainly wouldn't be too surprised. Now I have to put one of those disclaimers. Just my opinion.

The boiling point of gas can be as low as 85 or 90 degrees. That's one of the reasons they have summer and winter blend. Raise the vapor point for gas. In the old days the gas pumps at the station had the pump on the island and they would suck the fuel out of the tank below. (now there are under ground pumps and above ground dispensers but the term has stayed) Vapor lock was very common then as vacuum ;owners the boiling point just like pressure raises it. Can you remember in the old days the station owners hosing down the asphalt over the tank. It wasn't necessarily just to keep thing clean. He had to cool the area to be able to get the fuel sucked out of the ground. Yes ethanol boils even easier. Ever notice how quick an injury dries when alcohol is put on it? The little pressure that the tank hold helps some but it ain't much. I'm just guessing but I think it's like 1 5/8 degrees for every PSI of pressure but don't quote me on that number but that is the jest of it. So 3 or 4 PSI is no big deal(our bikes) then again cars with 30 PSI is significant. Remember vapor lock when the fuel pump was on the engine and it had to suck fuel the length of the car? (lowering the vapor point even lower) The only thing was they had no ethanol back then.

 

[redwing52]

I can remember people snapping clothes pins on the fuel lines thinking that would dissipate the heat. I always had doubts about that but who knows. Drag racers used a "cool can." A coil of copper tube inside a coffee can. Then route the fuel through it and fill the can with ice. Had to chuckle at those who put it way up front of the car. Fuel would vaporize before it got to the cool can.