Fuel Delivery? Vacuum? Can't start!!

[ahbilly]

I've got a 79 XS1100 that came to me in boxes. After spending about 3 weeks putting her together by the book, I ran into about 5 million problems that required hunting and searching for XS specific answers(ignition modules going bad, carbs needing "triple clean", etc) and ACTUALLY managed to sort them out and get the bike to run for about 2 hours. I rode to the parts store, and got some new vacuum and fuel lines and then came back. After installing them the bike would NOT start to save my life. I figured maybe the carbs needed to be sync'd up so I took them to my neighborhood shop that loves these old jap bikes and they had her up and running on another tank(but using the same fuel lines). As soon as I put my old tank back on though I can't get any fuel into the cylinders. The float bowls fill up fine, but dry cylinders all day long. I checked the petcocks and they let gas flow all day long in prime. I have bypassed the octopus and run vacuum lines straight from the carbs to each petcock, but like i said it ran earlier in this config, so i'm wondering WHAT THE HELL changed?

any insight would be greatly appreciated!!! I've had a non running bike for 3 weeks now and it would look a lot better on the road than in the garage!

Thanks much in advance!

[AlanB]

Hi ahbilly,

Need more info on the bike!

Specials have the octy, with a vac line to it, and dual outlet taps without a vac connection..
Standards do not have an octy; they use vac taps with a single fuel line per side to the carbs, and a vac connection per tap.

One way or another, you have the lines on wrong..... there are several "maps" for the lines on here (and if it IS a Special, there should be one stuck to the base of your seat!........)

Fuel lines are 1/4", vac lines are noticeably smaller.

the '79 will have two fuel inlets going to the carbs near the float bowls from the cocks, PLUS two breathers (similar size tube!) from higher on the carbs to the airbox.

Welcome to the forum; the answer is on here somewhere..... start at the "Tech Tips" section!

AlanB

[ahbilly]

standard?

I'm not quite sure WHICH model it is(seems like it might have been a mix of parts, but it didn't have an octy in that mix and I've set it up with the one vacuum line and one fuel line running from each petcock. left fuel line runs to the bottom inlet in between carbs 1&2 and the vacuum line goes to the top inlet. same for the right side in between carbs 3&4.

[prometheus578]

Yup, it's vacuum.
If I read you correctly, and you've written a correct description of where you have the lines going....

left fuel line runs to the bottom inlet in between carbs 1&2 and the vacuum line goes to the top inlet

Which top inlet do you speak of?
There are three inlets for hoses on these carbs.
Carb #2 has an extra one.. that is for the vacuum advance unit.
On the airbox side of the carb, the lower fitting, like you have stated is for the fuel line.
The "T" fitting above that is for the vent hose which routes to the airbox.
The vacuum lines for the petcock are attached to the fittings that stick out of the carb holders/manifolds on the engine itself.
From your written description, it sounds like you have vacuum lines to the petcocks coming from the carb vent fittings.
There is no vacuum there.
And if you have "open" vacuum fittings on the manifolds, you will draw no fuel from the carbs as the vacuum from the downward moving pistons will suck air through the open fittings.
keep us posted.

[John]

The vacuum lines should be connected to the smaller port on the petcock. The upper set of T fittings on the carbs are to be connected to the small nipples on the front, top of the airbox. Those are the bowl vents. What you are doing is essentially applying vacuum to the bowl area, when it needs to have atmospheric pressure on it.

[TopCatGr58]

Hey Billy,

You've got the hoses on wrong! The upper inlets on the carb bodies are JUST VENTS, not vacuum lines, and they are to go to the AIR BOX ports IF you have an air filter box. The vacuum lines for the petcocks...IF you have a STANDARD tank....it has the knee indents close to the seat, those vac hoses go to the SYNCH ports on the intake manifolds. The other fuel supply line....the one you get fuel out of on PRIME goes to the LOWER Carb "T's" only!

Now, you said you got rid of the OCTY! IF so, then you have a SPECIAL...tear drop tank, 2 fuel outlets on the petcocks.... they are pure gravity feed petcocks, fuel will flow out of both depending on where you set the petcock handle! Cap off the one that flows with PRIME, and use the one the flows with ON!!!

T.C.

[AlanB]

Hi Billy,

If you give us the first three digits of your frame or engine numbers, ( they were the same from the factory!) We can tell you what the bike is, and solve half of your problems.

If you can figure out how to post up a pic, we can probably clear up the rest! LOL!

One way or another; the general opinion follows all logic; the lines are routed wrong! You mention "the Book", so I guess you have a manual. The answer is in there somewhere!...... It is also in the tech tips on here.

AlanB

[prometheus578]

"Two moderators and the big administrator, himself!"

From across three different time zones....
All replies came within a four minute time period just minutes after 7:00pm.
What does this all mean?
It means that, across the country, city by city, zone by zone...
Oprah's show ends at 7:00, at which time, XS11 big-heads turn off the TV and look for other things to do.

(Thanks for pointing this out to me, T.C. I think we're just waiting now for Diver Ray to link into the XS11 conference call so we can discuss the latest on how we can get in touch with our inner feminine side. Plus, there's her new recommended book, etc)

Oh, and welcome to the site, AhBilly.
And yes, this is how we do things here. Information(or mocking abuse) is always free and free flowing.

[thewiz]

An totally EXcessive amount of MC prowess have you garnered on this thread !! The force is with you ...

[jgw1986]

Originally posted by TopCatGr58
Hey Billy,

You've got the hoses on wrong! The upper inlets on the carb bodies are JUST VENTS, not vacuum lines, and they are to go to the AIR BOX ports IF you have an air filter box. The vacuum lines for the petcocks...IF you have a STANDARD tank....it has the knee indents close to the seat, those vac hoses go to the SYNCH ports on the intake manifolds. The other fuel supply line....the one you get fuel out of on PRIME goes to the LOWER Carb "T's" only!

Now, you said you got rid of the OCTY! IF so, then you have a SPECIAL...tear drop tank, 2 fuel outlets on the petcocks.... they are pure gravity feed petcocks, fuel will flow out of both depending on where you set the petcock handle! Cap off the one that flows with PRIME, and use the one the flows with ON!!!

T.C.

OK, you guys are helping me understand my problem... I just need to clarify. I have an octy I'm pretty sure...(on top of carbs, four lines all numbered going in diff. directions). BUT I have the teardrop tank, im guessing the special tank, that is NOT made to be used with the octy? my airbox is garbage, so I was going to go with pod filters... my biggest problem is figuring out WHAT lines go where???the two noticably larger lines that attach to a T-fitting between the two pair of carbs... these are the supply lines? now what do I do with the four lines coming out of the octy? and what is the best route to go with the carb vent without an airbox?

I'm fairly concerned about this because tonight while working on it trying to figure out where these lines go, had a little fireshow. I'd heard these bikes have a fire problem but MAN didnt think it would go up that quick... got it put out really quickly tho and didnt ruin anything other than my velocity stacks... they were trashed anyways.

thanks for all help ahead of time! I just bought this 1979 xs1100(sf according to the serial #) for a good price... just trying to get it on the road.

[John]

Let's sort this out

If you have a Special, it will have the teardrop tank, and an octopus. Throw the octopus as far as you can and just leave it there until you are finished with the carbs. Now, back to the carbs...if the bike truly is a 79 then it should have two sets of T fittings between #1&2 carbs, and between #3&4. The set that is closest to the float bowls is the fuel inlet. The other set is the bowl vents, and is supposed to be routed to the two small nipples on the front/top of the airbox. If you should eliminate the air box, then you should route these lines up under the tank, and shove a small filter in each line. They must remain open to atmosphere. Now, on to the petcocks...
The front nipple on the petcock is the prime position, and it can be capped off. Run a fuel line from the right side petcock to the left side carbs, and vise versa for the other side.
Now you can retrieve the octopus before you run it over with the first mowing of the season. Place it in the nearest trash can. You are done with it.
If you should want to use an airbox, I can fix you up, and I also have some OEM velocity stacks, if you need to replace them also.

[AlanB]

Hi Billy,

What John said!.....Once you have thrown the octy away, there will be an open nozzle on the No2 carb boot. You need to get a cap for it, just like the other three have.

The easiest way to cap off the two front nipples on the petcocks is to run a line across from one to the other.

The octy is designed to shut off the fuel when the engine is not running; once you have removed it, the fuel does not shut off automatically, so get into the habit of closing off the petcocks when you park it!

AlanB

[John]

Alan, better than a hose connecting the prime ports is just use a 1/4 inch vacuum cap on the nipple. Good snug fit, and the rubber won't break down fom exposure to fuel. The vacuum nipples on the carb boots are 3/16 inch.