I have a 2000 suzuki katana gsx750f and it is having some\ntrouble. It floods...a lot. So, at first I thought carbs...but now\nI'm not so sure. I think it may be the vacuum actuated fuel valve or\npossible the tank vent. So, I'll tell you all what I did to\ninvestigate and all advice is appreciated.\nI started by removing the tank. When the fuel line was\ndisconnected, gas sprayed (with decent pressure) out of the main fuel\nline. Shouldn't the valve have prevented this? I think the tank may\nbe over pressurizing and forcing fuel past the shut-off valve. It is\nsupposed to be actuated by carb vacuum, so I figure the spring is\npretty weak and an over pressurized tank would fairly easily get by\nthis valve. Is this a correct assumption? Once I opened the gas cap\nto relieve the pressure, the valve stopped the flow of fuel on its\nown.\nNext, I removed the airbox after draining the fuel out of it\n(severe flooding). Then, With the carbs exposed, I tried a trick i\nread about here. i hooked a little piece of fuel line to each of the\ndrain nipples on the four float bowls, pointed the hose up and opened\nthe drain valve to check the float levels. They all looked pretty\neven. I kept fuel in the line from the tank to ensure that a bad\nfloat would show here. It didn't as far as I can tell. So, I pulled\nthe carbs, set them on the work bench at approximately the same angle\nand let them sit, with fuel in the fuel rail, to see if any of the\ncarbs was leaking gas somewhere. I didn't see any.\nNext I removed the plugs, and eureka! plug 2 was darker than the\nrest, so i assume this is the flooding cylinder, as the plug was\nbrown. So, I know which cylinder, but now why. Checked the carbs\nagain, still no gas leaking out.\nHere is my theory, and please tell me what you think. I think the\ngas tank is overpressurizing. The gas cap threaded and comes out\npretty hard sometimes. I think that this over pressure is forcing\nfuel past the fuel valve and past a float valve, flooding the\ncylinders and airbox. Is this possible? How much pressure should be\non the tank? How do i check it? Is the vent supposed to regulate\npressure? I am hoping to avoid taking the carbs into a shop due to\nthe expense. I would like to investigate all other possible causes\nfirst. Thanks for everyone's help!