Wierd fuel leak problem

[yupoo]

So my left carb used to pour fuel pretty bad. I would start to run out of gas it seemed and pull over, then it would start running over. Tapping on them sometimes helped. The left one was the one giving the most problems. So i rebuilt both of them with rebuild kits and the left one is still leaking sometimes. The other problem is i can only run my bike on prime but it will idle on ON/RES. It will run fine till i get hard on it (80-90mph) then act like it is not getting enough fuel and i will have to pull over and put it on prime to start it again. I've found an easy fix just by riding it around on prime. So obviously my fuel valve needs to be replaced. I ordered one already but what is causing my carbs to leak? The left carb leaks probably about a coffee cup size radius on a paper towel/day just sitting in the garage. but if i put the fuel valve on prime, it pours fuel like a drip every 2 seconds. Is it the fuel valve that would cause the carbs to overflow? or could it be the floats not regulating fuel? The fuel is coming out of the left carb drain hose

[scratch]

When you replaced the float needles, did you adjust the float levels?

[dgyver]

carb overflow = the float needles are not seating. Replace the needles and seats together.

[scratch]

The o-ring on one of the seats could be bad.