Carb vents.

[Glyn.G]

Hi all, I have a GT380 and have just noticed a small amount of fuel dripping from the carb vent pipe when I stop the engine. My first thought was it was one of the three carb overflow pipes, but on close inspection it was coming from one of the two air vent pipes. It only seems to happen when I turn the ignition off and it's only a small amount which stops almost immediately. I'm just a bit worried that if it's dripping when I'm riding it may be getting onto the rear tyre. Should I just bin the two pipes then if it does drip it's only dripping on the engine.

[Coyote]

Right or wrong. I never put hoses on those vents. Try removing those hoses and test ride again. What might be happening is those hoses might be drawing a vacuum as you ride - pulling fuel up. There should be no fuel there. Their purpose is to balance the atmospheric pressure in the carbs. I am a little confused how fuel can even get in that circuit.

[Craig380]

If the carb floods then fuel can flow out of those vent tubes. It could be that the float level is a touch too high, allowing the floatbowl to fill a bit too much.

But I wouldn't worry about that now -- as Coyote says, you can remove the tubes without any negative effects and see if it makes a difference. The tubes CAN get pinched and stop atmospheric pressure reaching the floatbowls, especially when the material is old and hard.

[pearljam724]

Flooding due to float height too high or contamination in needle valve seat. Has your tank been sealed ? Do you have an inline filter ? Check plugs for wetness.

[Glyn.G]

Cheers for all the advice,
I do have an in-line filter fitted, and I have decided to remove the air vent pipes as suggested. I've just realised that since fitting a set of expansion chambers the pipe that was dripping was actually touching the centre exhaust, could this have caused a vacuum as suggested as it never dripped when the original pipes were fitted.

[Coyote]

The hose just touching the chamber should have no effect other than possibly melting the hose. What I was thinking that rapid air traveling across the hose opening can create a vacuum. Remove the hoses and see if it still drips at shut down. If it does, I'd zero in on the floats next.. But really, that excess fuel should drip out the bowl overflow.before it gets anywhere else.

[pearljam724]

Sometimes the bowl overflow is the first place to clog on a set of carbs. They clog very easily, even with an inline filter if the tank is in need of being sealed. The smallest particles of contamination will float on the fuel surface that has by passed a filter. This is the reason I like to keep hoses attached to my overflow nipples. On occasion, you can grab each hose and exhale into them to clear the overflow without having to remove the carbs from the bike. If that would be the case, the next route of exit would be the carb vents. If the needle valve were clogged. Fuel would exit over flow. If over flow were not clogged. Sounds like you have contamination issues.