How to test float valve

So i've got my 03 300ex about 90% dialed in but it still acts like its flooding if i shut it off and try to start again. The only way i can get around it is to shut the gas off 1st and let the engine die. It sounds to me like a float valve issue but ive cleaned it with a q-tip and used 2 different valve needles but the issue persists. These floats are not adjustable so i was hoping to find out a way to test its functionality to see if this is indeed the problem. Thanks in advance guys