boiling the gas in 14 KX 450

I do not have any answers for you but you need to provide some more info to get better feedback from the 4 stroke specialists.

What temperature conditions and altitude is this happening at?

Stock efi mapping? Don't the Kawis have different mapping couplers, which are you running?

Have you tried any of the heat reflecting material on the underside of the gas tank?

Does it happen riding MX motos or on long off road riding conditions?

Idling in city traffic?

http://www.motosport.com/dirtbike/heat-barriers?psreferrer=http%253A%25…

Look at these. They would put a barrier between the engine and the fuel tank. The pro's use this set up in the outdoor races just for the reason of vapor locking due to the fuel getting hot.

You probably won't have an issue in the summer. The fuel supply this time of year is still winter blend which is more volatile than summer fuel. On a warm day winter fuel will boil more easily. You could try a different station, there may still be a few in your area that don't use 10% ethanol.

Weird.

I had the same problem on my 450 at anything above 80 degrees, especially second moto. I covered the bottom of the tank with the adhesive heat shield in the links above and wrapped the gas line as well. I rode a couple of 95 degree days with no issues after that. I had a different bike than you, but I would go there first for under $30 since it cant hurt.

Maybe a dumb question, but how do you know it was boiling? I'm assuming you ran out?

Sleepy Hollow?