Carb Setup Doubts

[SSthis79]

Hello all this is my first thread here in the forums about my first bike ever. Its a 79 xs1100 standard, picked it up about a month ago and hasn't ran in two years. When I got it, it had no fuel hoses connected so I bough a service manual and attempted to connect everything again, but I have some doubts.
First Doubt: There are two inlets to the carbs. One for fuel and the other is the vent? Also which is fuel upper or lower? I'm assuming its upper
Second Doubt: From the fuel diagram, I see the "octopus" valve receives vacuum from the engine but I am not entirely sure if the line goes straight into it or into one of the carb boots.
Thanks in advance guys looking forward to getting this setup correctly and firing her up.

[kboehringer]

Hello all this is my first thread here in the forums about my first bike ever. Its a 79 xs1100 standard, picked it up about a month ago and hasn't ran in two years. When I got it, it had no fuel hoses connected so I bough a service manual and attempted to connect everything again, but I have some doubts.
First Doubt: There are two inlets to the carbs. One for fuel and the other is the vent? Also which is fuel upper or lower? I'm assuming its upper
Second Doubt: From the fuel diagram, I see the "octopus" valve receives vacuum from the engine but I am not entirely sure if the line goes straight into it or into one of the carb boots.
Thanks in advance guys looking forward to getting this setup correctly and firing her up.

SS79,
RE: First Doubt:
Fuel ENTERS the carbs between #1 & #2 AND between #3 & #4. They are black fitting "T's" between the carbs just above the fuel bowls. That's where the fuel is plumbed. The upper are the VENTS. They should be hosed to the air box.
RE: Second Doubt: The hose to activate the OCTY is plumbed to a carb boot and then directly to the back port on the OCTY. I believe in stock form it goes to #2 but it really doesn't matter. The #2 CARB has a port on it that is used for the vacuum advance mechanism. The #2 is the ONLY carb with that port and it is the only place you can put the Vac Advance.... Don't mix those up!

KURT

[bikerphil]

The lower T's are the fuel inlets and the upper T's are vents on the 78-79 carbs. There is no octy on the Standard model bikes, they use vacuum controlled fuel taps instead.

[MaximPhil]

Hi SS,
Standards do not have the Octy.
So do you have the bike identified correctly?
On a standard tank the petcock has two outlets. The one pointing down is for the fuel line and the one pointing forward is for the vacuum hose.

Pictures help a lot. we love pictures especially of XS11's and their parts

Welcome to the madness
Phil

[kboehringer]

There is no octy on the Standard model bikes

OOOOps.... Missed that he said STANDARD.

[SSthis79]

I jus checked my vin and its a sf model not sure what the difference is

[cajun31]

The SF means you have a 1979 xs1100 special and is the reason you are dealing with an Octy. The specials had that.

[motoman]

I jus checked my vin and its a sf model not sure what the difference is

That be a 79Special, which originally had the Special tank and used the 'octy'. By your original statement about the petcocks, that makes the fuel tank original. The petcocks are different between the Special and Standard fuel tanks. Petcocks are NOT interchangeable between the two tanks either. Connections on the Special petcocks are different and have different functions between the two models also. If that wasn't to confusing for ya', there are those here that own the Specials, and are way more familiar and can make hooking fuel lines and vacuum lines up correctly less confusing than I would.

[mack]

Seems

like your questions have been answered. Most of us with specials get rid of the "octy" all together. It simplifies the plumbing a great deal!

[SSthis79]

Yeah after messing with it for a while I think I want to get rid of it. Would any of you guys mind drawing up a fuel line diagram without the octy? Not entirely sure how it would go.

[TopCatGr58]

Hey there,

You need to EDIT your profile/signature and change your bike from 79F to 79SF if you have the octy.

Next, the front nipples of the petcocks are just for the PRIME function, won't be needed, so you can cap them off. Next, run the fuel line from the right petcock across to the LEFT side carb bank pair and connect to the carb inlet. Do the same for the left petock to the right side. Good idea to put an inline filter between petcock and carbs. Try not to have the line drop too far below the carb inlet to help facilitate flow. Also, if worried about the petcocks failing/leaking you can put an inline cut off valve also.

The vacuum line from the Octy to the carb intake can be removed, and just cap off the sync port on the carb intake.

I thought we had an image diagramming this process, but can't find it amongst the tech tips, but the above description should be easy to follow.

T.C.