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Carb Hose Clarification

  • Thread starter Thread starter rickt
  • Start date Start date
R

rickt

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I've searched and studied the postings for connecting carb hoses and haven't found a match for the carbs on my '78 GS750C. The main fuel hose connector is obvious, but there are identical connectors on the carb bodies of 2, 3, and 4. I assume one of these must go to the vacuum port of the petcock, but which one???

Thanks,
rickt

Maybe a picture will help. The three circled in red (R) are my source of confusion.

GSCarbs-1.jpg
 
Last edited:
The port on #3 goes to the petcock, the other two have vent hoses attached that travel up over then down the back of your airbox. I have some pictures somewhere I'll try to dig one out.
 
The one on number three is the vacuum port to the petcock, the identical looking ones on two and four are float bowl vents.
 
all 3 in red appear to be float bowl vents. the vacuum port is identified by a direct hole into the engine side of the intake tract. as you can see the marked red ports are connected into the float bowls and 1-2 share a small rubber hose connecting them #3 and #4 have their own spigot as #3 is the "base" carb

under close inspection you will recognize how the casting is and how the passages are drilled.

a vacuum spigot port is just a hole into the intake. identifying it is really simple just spend a few minutes tracing the passage castings for experience sake.

on some years of carb banks (kawa and suzu1000s') one of the spigots in red is a vacuum and the other 2 are vents however telling them apart is a snap using brake cleaner and watching where they go from -to straight into the throat - vacuum... into the bowl - vent
 
Hi, as I remember, the third nipple has the hose which goes to the petcock. You can tell by looking inside of the bore for that carb, you will see a drilled hole, where the other carbs don't have.:D
 
Here you go Rick. These pictures were taken as the rack came off my 850 for cleaning with all hoses still attached.

PC204781.jpg

PC204780.jpg
 
Thanks to All

Thanks to All

Looks like #3 is the winner! Thanks for the quick and detailed responses.

Since I'm on a roll, I'll ask one more - on the rear, right side of the airbox is an enclosed clip (for lack of a better word). Looks like it was designed to have a hose or two running through it. It is meant for the vent hose from the #4 carb after it passes over the top of the airbox?

Thanks again.
rickt
 
rickt said:
Looks like #3 is the winner! Thanks for the quick and detailed responses.

Since I'm on a roll, I'll ask one more - on the rear, right side of the airbox is an enclosed clip (for lack of a better word). Looks like it was designed to have a hose or two running through it. It is meant for the vent hose from the #4 carb after it passes over the top of the airbox?

Thanks again.
rickt
Click to expand...

Vent hose from 2 and 4 both go under that "clip"
 
Two for Two

Two for Two

If my luck holds, I'll get the third answer to my carb tubing questions.

Attached is a picture of a hard plastic piece that was in one of the coffee cans that were used by the PO to store the carbs for my gift '78 GS750C. It has the look of a tubing loom, possibly for the vent tubes that come off the four float bowls?

Any thoughts on this one?

Thanks,
rickt

P1010049.jpg
 
rickt said:
If my luck holds, I'll get the third answer to my carb tubing questions.

Attached is a picture of a hard plastic piece that was in one of the coffee cans that were used by the PO to store the carbs for my gift '78 GS750C. It has the look of a tubing loom, possibly for the vent tubes that come off the four float bowls?

Any thoughts on this one?

Thanks,
rickt

P1010049.jpg
Click to expand...

That is an interesting piece, and does not look stock to me. I have not seen that on any of my bikes. Home made I would guess. I speculate that the PO wanted to collect all the drain & vent hoses int a neat package(4 bowls & 1 from the tank).
 
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