What are vent hoses?

[450racer17]

So I basically understand how my keihin pwk carb on my Ktm 150sx works but a bit conused on vent hoses??

Recently, the hose coming out of the middle of the carb on the exhaust side flopped off and it appears that gas was coming out of there while I was riding because theres a lot of residue on my tranny.

I thought they were for venting air?.. then I start thinking and wouldn't they want to suck air into the engine?

Can someone explain the concept behind these hoses please?

[The Spanky]

The carburetor uses the pressure difference between the atmosphere and the intake tract to cause fuel to flow up the jets and into the air stream. The float bowl has to be vented to the atmosphere so it can stay at atmospheric pressure. The tranny also is vented to the atmosphere to relieve pressure build-up.

The area above the slide is also vented to the atmosphere so that the slide moves freely.

The gas that spilled onto your engine came from the float bowl overflow drain.

There are no vent hoses that connect directly to the intake tract, so dirt doesn't get sucked into the engine.

[450racer17]

check it out

this is the one that flopped off

Your sure gas comes out of this one it seems a bit high

thanks for your help

[FrankV]

check it out

this is the one that flopped off

Your sure gas comes out of this one it seems a bit high

thanks for your help

No, that's an air vent.

The only hose fuel can come from (the one Smokey meant) is the float bowl overflow drain, which is located under your float bowl, so that's where the fuel on your tranny came from.

[cyrusgsxr]

gas can come out of there after an off , if the bike goes on its side ie carb tilted too far its normal and hence the reason the vent tubes are so long to route it away from exhaust etc