where is this fuel coming from?

[blitzstrasse]

I just got a '79 xs1100 yesterday.

When I moved it out of the garage this morning, I noticed it left a small puddle of fuel.

I couldn't find a source for the leak (if it IS a leak), and the manual said nothing about whether the dual petcocks should be set to OFF when the bike is not in use for long periods, such as overnight.

Any thoughts?

Thanks.

[xssiveone]

If it is a Standard model, there should be no "off" position. The fuel flow is vacuum controlled, when the engine is not running, there is no vacuum, if the vacuum control is working properly, the petcocks should be off. An easy way to check this is to remove the fuel lines from the petcocks. There should be no fuel flow. If there is, then a rebuild is in order.

If you have a Special model, then you will have an "octopus" that controls the fuel flow. Same thing applies, if the engine is off, there should be no fuel flow.

As to where the gas is coming from, it could be a cracked fuel line, but most likely it is your float valves in the carbs that are not shutting off the flow of fuel. This could be due to wear, or dirt on the needle or seat. You could try some carb cleaner, SeaFoam has produced good results, thru a couple of tanks. Might be enough to clean it out if it's dirt.

You could also try parking it on the center stand overnight. Sometimes this is enough, as a temporary stop-gap measure, to stop the fuel leak. Make sure your oil hasn't been contaminated by fuel as it will lead to serious bearing damage.

[Ken Talbot]

Just to add to Brian's note:
- if you have a Special, both the octopus and at least one of the float valves are leaking
- if you have a Standard, at least one of the petcocks and at least one of the float valves are leaking

There is no shortcut that lets you fix just a petcock/octopus or just a float valve. You need to both.

[skids]

Basically, two things must fail on a standard modle to make the floats leak:

1. Either the floats/needle seat is not sealing for some reason (corrosion in the float pivots, crud in the needle seat, stuck needle spring, sinking float due to a hole, bad o-ring around the fuel valve that contains the needle seat for later model carbs of 80's and 81's) AND,

2. the petcock is allowing fuel to leak passed it when in the RUN position. You are not storing the bike on PRIME, I hope.

Personally, I wouldn't store the bike on the center stand unless you elevate the front end, or it might leak fuel into the combustion cylinders and contaminate the oil.

What you can do as a temporary fix, is the following:
1. Unhook the two vacuum tubes to the manifolds.
2. Blow air into the tubes to the petcocks to force the internal plungers to seat (if that is the problem).
3. Unhook the vacuum tubes from the petcocks and put golf tees or something else in the ends to seal off air and then hook the other ends to the manifold nipples.
4. Use your petcocks in the PRI position to run the bike and remember to switch them to RUN when you want to turn off fuel flow.

This temporary method will not work if the holey gasket is shot in the petcock(s), or if the oring or conical seat in the petcock is buggered up. If this does not work to stop the leaking, I suggest that you drain the tank to prevent the fire hazard, and wait for new parts.

If you have a rust particle in one of the fuel valve needle seats, you can flush it out by causing the float to go down and then allow the fuel to flow. You can do this by runing the bike with the choke on with the petcock in the run position and the vacuum hoses disconnected with golf tees in them (as described above) until you draw the fuel way down, and then switch the petcocks to prime for the flushing action.

Hope this helps.

[Steve Linderman]

Gas Leak

Hey Everybody,
It seems like this fuel thing is getting more-n-more common.
I have replied to at least 5 Posts lately about fuel leaking.

Let's start at square one...and we'll add to all the good advise already given.

The fuel system (on an XS 11) consists of: the tank, the petcocks (2) the fuel vacum diaphram(octopus on Specials) and the carbs.

the problem with fuel leaking can be: bad petcock to tank seal /petcock leaking/ cracked fuel line/ bad fuel vacum diaphram/ bad needle or seat.

Start from the top...put the "little arm" on your petcocks to OFF
raise the back of the tank and remove ALL fuel lines, if the petcocks "DRIP" then you have found ONE problem. Inspect All fuel lines AND connections at this time

next (if you have a Special) remove the little vacum line from the Octopus (the one going into the intake manifold) LEAVING the other end attached to the fuel vacum diaphram...then with your mouth suck on the end of the vacum line...hold the pressure for about 10 seconds...you should percieve NO leakdown...if you do, then you have found ONE MORE problem...
Now the internal carb parts are harder to "diagnose" without removal...but if you've found "problems" with the petcocks OR the Octopus...then you have found the source of the leak.
you know that something is "wrong" with at least ONE of your Needles or seats...as they are the "last line of defense" to preventing fuel from "flowing" when the motor is off.
I usually find that the left outside carb is the Culprit.

Fuel leaking is a BAD thing in any case...this is a typical scenario...
you ride the bike...and stop for a while...gas slowly drips into the airbox...and you don't know it...when you come back, you don't smell it and you start the bike up...it's only a "little gas" but the motor is being fed "unmetered fuel" and this will cause overheating...let's say you parked slightly uphill or used the centerstand...and the fuel ran forward...into the crankcase...when you start the motor...you "pollute" the oil and BEARING FAILURE can occur.
If you suspect fuel leaked into the crankcase...you can use this simple test to determine the severity...take a small stick or twig (about 10 inches long) remove the oil fill cap and insert the stick until it reaches the oil...quickly remove it and with a lighter try to light the OIL (AWAY FROM THE MACHINE) if it is PURE oil it will smoke and bubble...if it is "gas polluted" it will BURN like a "torch"
If the oil IS polluted DO NOT START OR RIDE THE BIKE!!!

If the bike is parked regularly on the side stand...and it has a gas leak...the fuel will flow "backwards" into the airbox or airhorns...the fastest way to determine which carb IS leaking...is to remove the airbox lower half...and stick your finger into each air horn (inside airbox) and feel for moisture.
The Wife-n-I have 3 Specials and only ONE doen't leak gas (YET)
so we "have a drill" we ACT like gas WILL leak EVERYTIME we stop
so before shutting them off we turn the petcocks to OFF and idle the bike for a few minutes to lower the fuel level in the carbs...leaving the margin of error in our favor.
there are several tech articles here about removing the Octopus and other fuel system "fixes"
but if you want to ride her...keep a "close eye" on that fuel leak...you may only get ONE chance...if you fill the airbox...and the motor "sneezes" or "backfires" you could "blow the motor" or start a BIG FIRE...
Unfortunately "turning off the gas" will not always "turn off the gas"
Fuel should flow ONLY when the motor is running, or the petcocks are switched to PRI (I said SHOULD) but in XSland that ain't always the case
Once you learn the components of the fuel system...repairing them isn't very hard...
Plus you got a slew of "X-PERTS" to help...and if you get "fed up" with it...one of us "X-sessive" people will probably buy it from you

good luck...welcome to the "club" and KEEP POSTIN'
Steve

[scalded dog]

I have rebuilt my petcock once already, and just finished building it again, If the petcock has been rebuilt how would gas leak past it , where the float needle could be a problem. I havn't figured out why the first kit didn't work. Any help appreciated. Later 'Dog

[Ken Talbot]

If the spring has become weak (i.e. permanently compressed a bit), it might not be pressing the o-ring hard enough to completely stop the fuel flow. If you remove the fuel line from the petcock, does it still dribble when there is no vacuum applied? Maybe try stretching out the spring a bit before reassembling and see if that makes any difference. If it does, you might need to find some fresh springs.

[scalded dog]

Thanks Ken, the spring seems to be strong enough, but I have several springs, that I can try,btw, do you know where I could buy new ones. Later 'Dog

[skids]

I tried stretching one of the petcock diaphragm springs on a model E and now, I have occasional problems with fuel supply at 70 mph. I guess the spring is now a little too strong with that available vacuum. I now have to switch my left petcock to prime if it starts cutting out...

[scalded dog]

Steve, thanks for th tip about the stick. I tried it this morning on all three xs 1100s I have, the only one that caught fire was the one, I have been having trouble with, this is a great sight. Later 'Dog

[scalded dog]

I rebuilt the petcocks again left tank sitting with gas in it, all day, I had no leaks, I put the tank back on the bike, the next day I checked the oil level to see if it had raised again, it had, checked the oil with stick, it has gas again, I went to the hardware store to see what I could find, I found some plastic in line fuel shutoff valves, I put them on and will check the oil again to see if they work. I will post results later. Later 'Dog

[skids]

If you are now using hardware store manual petcocks, it is probably a moot point... but...When you rebuilt the vacuum diaphragm, did you polish the conical section where the plunger seats with its o-ring? The special diaphragm is at the octopus, the standard is at the petcock (by now I am SURE you know that!).

Also, I noticed that some orings tend to bulge on one side when placed in the groove on the plunger, and this would cause an imperfect seal.

[strom]

Now im pissed

Im gettin me a carb and petcock repair kits, and some new brake caliper seals, if get any. Dunno what Im gonna do bout the crankcase leaking yet.

LP

[scalded dog]

Skids, I did not polish the seat for the o-ring, I may take it back apart, and give it a whirl, petcock kits and oil is getting expensive. Later Scalded Dog

[skids]

I'll tell you another thing you can do to make the petcock last longer... The handle valve is milled rough from the manufacturer. I think this can cause excessive wear on the holey seal. If you are going to polish the conic seat area anyway, you might consider smoothing and polishing the handle valve. Fine grit emery cloth, followed by mother's milk polish (or similar) will give it a mirror-like finish. I also tried to reduce the "cutting" egdes of the holes just a little. I think leakage of gas, due to a bad holey gasket, could cause a petcock to leak into the carbs. Sometimes, the gasket can be rotated to a better position (bad hoe to the top?) to stop leakage. The wavey metal gaskey can also be rebent to apply a bit more pressure of the handle against the holey gasket.

Originally posted by scalded dog
Skids, I did not polish the seat for the o-ring, I may take it back apart, and give it a whirl, petcock kits and oil is getting expensive. Later Scalded Dog