Topic: CB550k Carb Vent

[7]

Does anyone know the purpose of the vents (circled in red on the picture which I borrowed from the internet)? I find it odd that they are linked between each carb and then vented to atmosphere? Thanks for the help.

-7

https://imgur.com/aF1UgK5

[uksparky]

Does anyone know the purpose of the vents (circled in red on the picture which I borrowed from the internet)? I find it odd that they are linked between each carb and then vented to atmosphere? Thanks for the help.

-7

https://imgur.com/aF1UgK5

Float bowl vent, if they were not there fuel would not flow the the carbs.... hold a bottle of water upside down with small hole in cap... see how slow the water flows.... now put hole in the base of the bottle....vented.. water flows faster...

[7]

Thanks! That might be part of my problem with fuel level. Maybe an ignorant question but wouldn't air escape via the jets?

[Bankerdanny]

Thanks! That might be part of my problem with fuel level. Maybe an ignorant question but wouldn't air escape via the jets?

Think juice box and straw. When you suck the juice out the box sucks in. Now imaging the box were aluminum and no air could get in around the straw, would you be able to suck the juice out?

Fuel is sucked up through the jet by the low pressure created by air moving through the carb throat, if there isn't a vent for the bowls then the fuel can't be drawn up through the jet just like juice won't make it up the straw.

[TwoTired]

Air has weight.  The column of air above you exerts about 14.7 PSI upon everything on earth at sea level.  It's what keeps blood inside your body, and allows you to breathe.

The carb bowl vent allows this pressure onto the surface of the gas fluid in float bowl.
When the engine's piston fall while the intake valve is open, air rushes in to fill the vacant volume, creating pressure negative to normal atmospheric pressure.  The fuel jet orifice now experiences a differential pressure across it and passes fluid, to be mixed with incoming air, into the engine cylinder.

Without a bowl vent, there would be no physical way for the fuel jets to deliver fuel, in the existing design.

Cheers,

[Little_Phil]

Thanks! That might be part of my problem with fuel level. Maybe an ignorant question but wouldn't air escape via the jets?

The vent ensures that doesn't happen, as it would interfere with the venturi effect of the carb.