help running gas line

[TopCatGr58]

Hey Edavi,

What's got you confused is thinking that these petcocks are vacuum controlled. They are GRAVITY feed, and your markings are correct. The Control Valve=Octopus IS what is the vacuum control mechanism. Both ports on the petcocks ARE for fuel flow, there isn't a vacuum port on them!! The Prime ports are for filling the carbs after extended sitting before engine is running. The other settings are for the other petcock port that flows THRU the OCTY and is controlled by it's function while the engine is running.
T.C.

[edavi394]

ok thanks I think I understand now. I guess I got confused after I looked at the post about testing the octi I didn't think gas was suposed to flow in the on position unless there was vacuum on it.
when I hook up the lines and turn the fuel on gas runs out of the airbox (I still have the bottom of) I thought maybe the needle valve was sticking and causing this. I haven't taken the carbs off and rebult them yet. (I cleaned them about 2 years ago and they have not had gas in them since)

[DiverRay]

You DO have the fuel lines running to the BOTTOM "T" fitting on the carb, and the TOP "T" fitting running to the "nipples" on the airbox, correct??

[edavi394]

yes I have that part right.

[DiverRay]

OK, As I can't "see" the bike, I need to ask...

[edavi394]

no thx for checking I did have to ask that question already to make sure how to hook it up. I took the gas lines off 2 years ago to replace them then I never got back to the bike untill now. so I didnt have any Idea how to hook them back up and looking at the picture I couldn't tell if they went to the top or bottom.

so let me ask this just to be sure. the only reason now for gas to be leaking out (since the lines are not leaking and the octy was rebuilt) is the carbs are sticking and need to be rebuilt correct?

[rbmgf7]

not to hijack this thread, but what is the purpose of the XJ fuel line? i take it it's some sort of vacuum assisted fuel pump? is it entirely neccessary? i'm just use to simple gravity fed carb systems. this is actually the newest bike i own. all my others are pre-78, lol.

[John]

The XJ fuel line is actually what we call the octopus. It is not a vacuum assisted pump, but it is a vacuum controlled fuel shut off/distribution valve. The vacuum is to open the diaphram inside of it to allow the fuel to flow. Many of us have ditched the octopus, and just run a line from one side petcock to the opposite side carbs, and capped off the prime (forward) nipple on the petcock. You won't need the prime function, because fuel will flowwhen the petcock is in run or reserve.

[TopCatGr58]

Originally posted by edavi394
so let me ask this just to be sure. the only reason now for gas to be leaking out (since the lines are not leaking and the octy was rebuilt) is the carbs are sticking and need to be rebuilt correct?

Essentially yes. Not so much rebuilt, but cleaned. If you rebuilt them with new parts a couple of years ago, but never put gas in them, then they should be okay. You may need to clean/polish the brass float needle and seat to ensure a good seal. Also check your floats for leaks, the almost boiling water trick. Also check floats for sticking to bowls, perform a bench test for leaks before mounting on the bike. Many recent threads and photos, a quick search should reveal them.

Someone posted that they thought you had rebuilt the Octy, but I didn't see where you said that, and so your other assumption is correct, fuel should NOT flow with the petcocks set to ON.....IF the Octy is working properly, but if it's corroded, rusted, etc., then it can leak and allow fuel to get to the carbs, where you are then ALSO experiencing a problem with the float valves, because it shouldn't flow out the carbs IF the floats are working and sealing right!!!
T.C.

[jjz28]

sorry to bring back such an old post but i just brought home my new to me 79 xs1100sf. I want to get rid of the octopus. So i run my gas line to the oposite side of the petcock. Is that so the line doesnt crimp? What about the other T on the carb, guess it will go to airbox to? Thanks guys.

[natemoen]

If you are eliminating the octy you just need to connect a fuel line to the "on" nipple (should ve the rear nipple but check cause the petcocks could have switched sided) and run the line to the fuel T, the lower one. Most people run the line to the opposite side T and put a small fuel filter in line. The other petcock nipple can just be blocked off as it is no longer needed.

The upper T on the carbs is the bowl vent and should be connected to the airbox.

[DGXSER]

Welcome JJ.

There are different schools of thought on how to run the fuel lines. Many folks run the fuel line from the left petcock to the right side fuel T, and vice versa. This added length is used to mount an inline fuel filter, and also give soem lack in the fuel line so the tank can be lifted without disconnecting the fuel line.

Personally, I prefer the KISS (Keep It Simple Stupid) principle, I just rin my fuel line straight down between the air box inlets on the same side, put an inline filter in that drop, and then right into the fuel T for the carbs.

whichever way you hook up the fuel lines, the vent lines (the upper Ts in your carbs) still hook to the air box nipples.

[jjz28]

I got my lines run after a lot of kinking and I know that my petcocks flow fuel but I cant get my left side to fill up. I have clear line and it has all kinds of air pockets in it. Is there a trick to getting these things run to get best fuel flow? Thanks.