Fuel system/carb problems! Please take your time to read it all.

[jaimes-duran]

How's it going guys? Well yesterday I went for a short ride on my 79 xs1100 special. I just got the bike 2 weeks ago and usually go for a short ride everyday. Well yesterday I started the bike with the choke b/c it was cold. I didn't let it fully warm up! I started out fine. I got down the road and opened the throttle a good deal and got a really loud popping noise in the mufflers. I went home and noticed gas leaking from the air box. I took the bottom off and there was a big puddle of gas in it. I tried starting it and it seemed like it was flooded with fuel. I also sniffed the oil in the crankcase and there was gas in it. So today I changed the oil. Took the gas out of the float bowls and turned the petcock valves to the off position disconnected the fuel lines and put a small container under the valves. I came back several hours later and found a large amount of gas in one container and a very small amount in the other. I reconnected the lines added more oil b/c the oils had then fully settled and went down. I started the bike and it ran with no problem. I opened the throttle and the loud popping noise was gone. I went for a short ride. The bike was fine it just cut off when you let go of the throttle. Although the idle screw is fully in! I cleaned the petcock valves and they seem a little better. The only thing bothering me now is the idling. Can anyone give me and explanation of why all of this happened? Also can anyone tell me if there's any other way to adjust the idling when the master idle screw is all the way in? Your time and concern will be greatly appreciated!

[jaimes-duran]

Also can anyone tell me how I can prevent this from happening again?

[tarzan]

It probably flooded because the fuel valves under the floats leaked.
That could happen because the valves are bad or there is debris in them or the bowls were empty and the floats got stuck on the side of the bowl.Then when you turn on the petcocks it flooded.
If it flooded as bad as it sounds like then you probably have gas in the oil.And if you run it like that it will burn up your crank bearings and ruin the engine.
So it may be well advised to do an oil change.
As far as your idle,if the idle screws are turned in till they seat to tightly then the screws tips break off and you will not get it to idle right.
So,it sounds like a carb cleaning is in your near future.
Oh ,welcome to XS11.This is the place where you can be talked through your own repairs by people who know and love these bikes.
Good luck. Rick

[DGXSER]

OK, the fuel system has two locations that control fuel flow. The petcocks start and stop fuel from flowing from the tank to the float bowls. Sounds to me like you tested the sealing of the petcocks.

The other location that controls fuel is the float valves in the carb bowls. This stops fuel from flowing into the float bowls when the fuel level in the bowl reaches the appropriate level. Fuel in the airbox and oil is the indicators that this/these valves are not working correctly. These valves should stop the fuel from flowing into the carbs despite the petcocks closing or not.

Sometimes, if the fuel level in the bowl drops to low, as in you let the gas run out or forget to open the petcocks and let the fuel run out in the bowls, then the float can drop to low and get stuck. Wrapping on the bowl with some type of screwdriver can loosen it.

Sounds like perhaps yours are sealing themselves now? I would still recommend you consider replacing the float valves and seats.

[Czekus21]

I know this is just a shot in the dark, but, do you have your fuel petcocks in the prime position? Is the plumbing correct with the dual feed petcocks/octopus? and last but not least, the floats correct?

[jaimes-duran]

yes I have them in the prime position. When I tested them like I mentioned earlier I noticed the only way I got fuel to flow through them was having it in the prime or reserve position. If I had to take a guess myself I will be leaning more towards the petcocks instead of the carbs. I just cleaned the carbs.

[Czekus21]

With the petcocks in the prime position, fuel will continue to flow. Till your out of fuel, and the crankcase gets real full. Good for cleaning all the gunk. bad for everything else. If you have the octopus set up, it will take vacuum to get the fuel flowing. As long as they're in prime, you'll continue to have this issue. Not a problem. It's supposed to do what they did. Try runnin the bike with the petcocks in the run position. If it stalls out, then we'll attack the real issue.

[DGXSER]

The special uses the vacuum operated flow switch between the number 1 and 2 carburetors. This valve when operatign properly does not let fuel flow into the carbs unless the engine is running. It can fail either open or closed. The prime position eliminates it. Also be aware that the prime position also eliminates the reserve function as it pulls fuel form the bottom of the tank.

If you have fuel overflowing the carb bowls into the engine and or the airbox, then you DO have an issue with your carb float bowl valves. This is not an if, it is so! The petcocks can not let the fuel into the carb bowls if the float valves are operating correctly.

Sorry, but you do need to go back into the carbs.

[jaimes-duran]

Thanks for clearing it up for me guys. Sorry I take a little bit to understand the fuel system but with the info from you guys I think I found the problem. I am missing a line on the octy. I looked at a diagram on the forum <http://www.xs11.com/xs11-info/tech-tips/maintenance/carburators/183-special-diaphragm-assembly-octopus-testing-and-fuel-hose-routing-diagram.html> it says that the line is the "Vacuum pipe". I guess this is why I am not getting fuel with the petcocks in the on position. So where does the vacuum pipe run to ecactly?

[petejw]

Just as Dgxser said, whether the petcocks are leaking or not,
fuel is getting past the needle and seat, this can happen when you've had the carbies apart because you end up disrupting the original position of the needle to the seat, pull the carbies apart again and clean the seat with a 'q' tip and some polish. reinstall everything back together again.

To check to see if they are sealing, with the bowls off turn the carbies upside down, the floats will now close the needle and seat, with a piece of fuel line on each fuel inlet, blow into the hose with ur mouth, if there are any leaks u will hear and feel it.

[Ken Talbot]

it says that the line is the "Vacuum pipe". I guess this is why I am not getting fuel with the petcocks in the on position. So where does the vacuum pipe run to exactly?

The vacuum line for operating the octopus needs to attach to a nipple on one of the manifold boots. It does not matter which one. Then make sure the other three are capped off.

[Larrym]

Yup! Just what Ken said. The "engine vacuum" is supplied by one of the nipples on the black intake boots which connect the carbs to the motor.

Methinks that possibly one of them is open/not connected to your octopus and that may be the reason you are having problems with your idle speed and "stalling" when you release the throttle.

The octy is the fuel shut off for this bike and if the fuel shut off is not working properly bad things happen. Test it again and if the octy shut-off valve isn't working then fix it. The float valves/needles/seats are not the fuel shut off and are no substitute for a proper off/on.

[jaimes-duran]

Thank you everyone. I will listen to all of your greatly appreciated advice and go for another try tomorrow. I am going to call it a night and get some rest. Thank everyone and hope to talk to you guys soon!

[petejw]

Just a note, by fixing the petcocks that should stop the fuel
from flooding when the bike is stationary, but once the bike is running
if the needle and seat arent sealing the bike will still run rich and poorly,
especially at idle.
Good luck with it.

[CatatonicBug]

With any fuel issue, ALWAYS start at the bottom, and work your way UP!

With a Special, there are 3 things that can stop the fuel flow, though usually, one of them (the petcocks) is not used. The Float valves are the MAIN thing that is supposed to stop the fuel flow. If fuel is flowing when it's not supposed to, there is DEFINITELY a problem with the float valves - guranteed.

While you're in there, work your way up the line and check the Octy. It looks like you already checked that, and determined that the vacuum hose was not hooked up correctly. Remember that when the petcocks are in the RUN position (which is where they should ALWAYS be, unless the fuel light is on, or you are doing a tuning check), the Octy is the secondary valve to shut off the fuel when the bike isn't running. You can check the octy by sucking on the vacuum port (yes, with your mouth) and see if fuel flows through the octy, then stops when you stop sucking on it.

The Petcocks should not need to be turned off unless you plan to park the bike for a while. They are there so you can remove the tank when needed, or switch to reserve when the fuel light goes on. Prime can be used when re-installing the carbs so fuel will flow to them before the engine starts. Once the engine starts, switch back to RUN.