JB Weld is GREAT stuff -- just make sure the surface is CLEAN and rough it up a little with wire brush or fine sand paper. Make sure it isn't so thick it is interfering with anything.
Picture of the crack ? - Video not necessary.
I am posting pics of the carb. Two things - 1) there is definately a pin hole where a scratch is, i think I can just JBWeld it, 2) there is a hole below it that has some scratches on it, I am wondering if this should be plugged up.