Topic: 78 550K one fuel outlet on tank, two inlets on carbs?

[rsvp9146]

 Putting the carbs back together and notice one larger fuel line feeds the floats and a smaller inlet that feeds all four carbs through rubber lines.

 I look at the tank and see the petcock has one connection for the larger line.

 So is this the wrong petcock or where does the other fuel line go? Is it a breather of some sort?

[Jonesy]

There is only one fuel line, the larger of the two. The other hose is the float bowl vent line. This goes up over the airbox.

[boatsdickson]

And connects to the airbox? What if running pods?

[Bodi]

It doesn't connect to anything, just a vent tube. I would just run it down with the overflow tubes.
You can tie it to the frame under the seat or just run it down with the overflows, I don't think it has to be up high but I may be wrong. Other bikes just have it hanging down.

[Swede]

There should be two fuel lines one feeds 1-2 the other 3-4.  If you only have one line coming from your petcock then you need to get a T fitting so that you can feed all 4 carbs.  There should be 4 float bowl vent lines that fit on the bottom of the float bowls.

[bryanj]

I thought the 78 only had one fuel line whilst the earlier, up to 76, had two

[gold01ca]

There should be two fuel lines one feeds 1-2 the other 3-4.  If you only have one line coming from your petcock then you need to get a T fitting so that you can feed all 4 carbs.  There should be 4 float bowl vent lines that fit on the bottom of the float bowls.

correct about the T fitting but the 4 lines under the float bowls are overflows not vents.
carbs 1-2 are vented with 1 line, same with 3-4, 2 vent lines total.

cheers!

[SteveD CB500F]

Bryan.  I bought a set of 550F (069A) carbs off eBay to go on my 550 engine which I aim to put in the 500 while the original engine is having the tranny fixed (complex eh?)

They have two feeds and a t-piece.  Did the 550F have a single outlet fuel tap?

How's the move going BTW?

[hondaryder]

The 78 550K has only one fuel line feeding the four carbs. Then each carb has a smaller overflow line attached to each float bowl. That is it.

[boatsdickson]

That answers a few things 4 me...My 78 k8 has the larger fuel inlet on the carbs fed by one line from petcock which is fine, but I couldnt figure out what the other inlet was for. I dropped a vacuum cap over it. Guess Ill go back and correct that.

[bryanj]

Steve, in all honesty I cant remember about the F but I suspect it was a single outlet with a screwed onto a "boss" petcock. I remember beging surprised some time back when I saw a screwed on petcock with two outlets on a US import (76ish 550K I think) as that was a type I had never seen before---since found out it is the rarest and most difficult to get and I have a horrible feeling i "binned" the tap but kept the tank DOH!!!