I noticed after filling up my tank the when i started riding the gas would seep down my tank? I don't fill it past the neck in the tank. My gas cap is new but do the caps on motorcycles vent? Or sealed like a car? After filling I only got 80miles before my gas light came on. Which is low so I thinking maybe some of the gas is evaporating because of the cap. The cap mounting screws are tight so not sure why it would seep. The fuel system is basically all new so I don't think its a carb issue. I usually keep the rpms in the 3,500 to 4,500. I haven't changed the plugs yet but I gaped and cleaned them when I was getting the bike together. (nothing unusual when i did that) I'm gonna check to make sure the choke isn't sticking on the carbs but I don't think so because the bike runs great.
I am 99 % sure 1 Gen vents through the cap.