Topic: 78 CB550 PD46C Carburetor Question (simple)

[VigCS]

Hi everybody.  I'm putting my bike back together and noticed two bungs on my carb rack (after disassembling/cleaning them).  I know the upper bung in the picture is for fuel, but what's the lower one?  What does it go to?

Thank you!

[Deltarider]

It's for venting to the air. Two adjacent carbs share one long rubber tube. There should be two of these vent tubes in the middle of the rack.

[VigCS]

Awesome, thanks!!

[Deltarider]

The K3/4 is full of tubes. Make sure when you route all vent tubes - beside the two mentioned above, there are 4 more venting tubes for the individual floatbowls - are not closed by the centerstand (retracted). Although it doesn't occur often, it has been reported the K3 in extremely wet weather can suffer from water that made it's way up into in the carbs. Remedy: cut a inch or two of the tubes, so they won't dangle too close to the road.

[VigCS]

The K3/4 is full of tubes. Make sure when you route all vent tubes - beside the two mentioned above, there are 4 more venting tubes for the individual floatbowls - are not closed by the centerstand (retracted). Although it doesn't occur often, it has been reported the K3 in extremely wet weather can suffer from water that made it's way up into in the carbs. Remedy: cut a inch or two of the tubes, so they won't dangle too close to the road.

Are you talking about the overflow tubes on the bowls?  There aren't individual vent tubes for the bowls on the 46C carbs.  I'm also fairly sure there's only one vent tube and it's the one pictured above.  Those are the only two bungs 'buried' inside the rack (fuel and vent).  I'll check the carbs tonight to be absolutely sure.

[MiGhost]

There will only be the one vent tube on carb 2 in the PD46C carbs. Carbs 1,3&4 are vented by the rubber tubes that connect them. The vent should route to top of the air box area. The four drain tubes are routed back along the case to the swingarm area.

[Deltarider]

There will only be the one vent tube on carb 2 in the PD46C carbs. Carbs 1,3&4 are vented by the rubber tubes that connect them.

MiGhost is right. Only one vent tube and four floatbowl draintubes. Do note what I post before.