Gas consumption is way too HIGH, Mileage too low

[GLoweVA]

Don't know what I would do with a set. Maybe someone else needs one of the others and is willing to go 50/50 with me.

I did an experiment, at Georges suggestion, with a wet/dry vac to see if I can find any leaks. I added some other steps in order to get measurements.

I opened the drain at the bottom of the carbs and attached a clear hose stretching it to the floor where I had a bottle of water. I then ran the vac on the intake simulating engine vacuum. The water level in the tube rose evenly for all four carbs about an inch. If I put my hand over the intake, the water level rose to a few inches below the carb on all but #2. It sucked in the water filled the bowl and into the chamber. I don't know if that means anything but are there any exterior vents on the carb?

Okay, this got me thinking. (did you plug up the port for the vacuum advance?)
There should be no external vents on the carbs. If there was then you wouldn't be able to suck the water up the hose.
With the butterflies closed, then the majority of the suction should be thru the pilot circuit. So, #2 drew more suction on the bowl.
I seem to recall a thread TC posted when he cut some carbs in half with his band saw. There's drilled holes in the sides where the different ports are made by the manufacturer. then they are plugged. maybe that's were the problem lies.

I'll have to ponder this some more.

Here's TC's thread:
http://www.xs11.com/forum/showthread...ight=carb+path

The drill holes have what look like ball bearings (or stainless steel BBs) pressed in the holes. If one of these is missing, then the pilot circuit would suck from outside the carb.
Just some initial thoughts.

[vedgar]

Need more time in the saddle

A three cylinder xs1100 feels flat compared to all four cylinders firing. The downpipe will be cold or cool to the touch. Ride a known good running bike to get a feel for what the performance should feel like. You will be amazed !
thanks ,
Vance

[RichV]

I now have a good set of carbs on loan to try. They seem to be running fine on the bike but I haven't been on the road yet.

After running it today at idle, I pulled the plug and it looks NORMAL now.

A ride will tell more.

As for the #2 carb, I've been all over it several times using the broken post #2 carb for a reference. I can't see any differences. The vacuum advance is connected.

[Bonz]

Any chance a diaphragm is somehow not lifting and leaving the main jet plugged by the needle? Or that the needle isn't lifting with the diaphragm? Lord, I know that's a huge stretch to even suggest that!

You have checked fuel levels in the bowls on the bench, so something past that point in the system may be blocking fuel coming up through the main jet if you are getting no fuel to the cylinder for the known spark to ignite.

[RichV]

Any chance a diaphragm is somehow not lifting and leaving the main jet plugged by the needle? Or that the needle isn't lifting with the diaphragm? Lord, I know that's a huge stretch to even suggest that!

You have checked fuel levels in the bowls on the bench, so something past that point in the system may be blocking fuel coming up through the main jet if you are getting no fuel to the cylinder for the known spark to ignite.

The diaphragms are raising the same on all four carbs on the bench with test pressure.

I tested the fuel levels on the bench, bike and running. That said, I'm going to try a test today to see if I can get it to fail on the bench.

[RichV]

Today I did a test ride with the replacement carbs provided by George and the results were very good.

The bike was responsive throughout it's range with no stutter, vibration, stalls or hesitations. No runs or drips.

A test of the mileage show 42 MPG which is twice the previous level.

So it's the #2 carb and I don't know why. I've swapped everything out.

For now I'm going to run with the replacement carbs so I can make sure the rest of the bike is okay or until George demands them back.

[GLoweVA]

For some reason, his #2 isn't 'sucking' any fuel into the head.
It works fine with the set i lent him, so we can rule out anything outside of the carbs.
So, there's something that's either leaking by thus not allowing enough suction to draw the fuel from the bowl or something blocking it.
He's replaced just about everything and cleaned them multiple times.
I was thinking about all those passages that are drill throughout the carb and one of them could be the problem, or the butterfly seals are shot.
Just a couple of thoughts.

[TopCatGr58]

Wow....I'm glad to see/hear that it was the carb, and not the engine/rings/valves!! PHEW!

Someone mentioned about the enrichener plunger not sealing...and that's what I'm thinking now. That's a VERY BIG hole/port that goes right to the vacuum slide chamber....and if it's not sealing....it could be allowing a large amount of air to get in there preventing it from being able to draw up the fuel!?

At least, we'll feel more confident in him making the XSSE rally and being able to make the whole trip without a major breakdown/problem!

T.C.

[Bonz]

Hmmm... Interesting idea TC. I thought of the enrichener plunger and no slide lift as potential separate issues, but didn't reason out that the enrichener could negate slide lift.

[RichV]

There is definitly something different about the #2 carb. I just can figure it out.

Today I shot carb cleaner through all the holes (including the 3 little ones) and it blew through. I replaced the plunger and spring in the enricher a while back and nothing changed. I even adjusted the slide bar to make sure it provided positive pressure when closed. I sealed the diaphragm edges and it tests and react like all the other carbs.

Something is causing little or no gas to come out of the carb or WAY too much. It doesn't start out this way, usually, and it takes about 20 minutes before things fall apart.

I've read and re-read all the tutorials on the carbs looking for something I've missed. Something is throwing this carb out of balance.

I will say this. The bike did not performed anything like what it did today. It's A LOT better.

Having George drop by helped a great deal. We were lucky that the problem showed itself right off the bat and he pulled the wire on the #2 plug and nothing happened and my tester showed that the plug was still getting power.

Tomorrow I will remove the floats (again) and pull the seats. I'll check the fuel passage for ANY problems and try to walk through the whole thing again.

[MPittma100]

In the Pile

I believe it is time to say goodbye to this problem carburetor. From what it has cost so far, it appears that it is simply a waste of time and $ to pursue further repair on it. Toss it in the pile and move on. Consider yourself lucky that it has not damaged the engine.

[Bonz]

RichV, you haven't missed anything that the rest of us haven't or wouldn't have tried ourselves in the same situation. The collective is XStremely stumped on this one too, you have the best XS minds in the world, literally, working on this with you.

Make an offer on that loaner set of carbs...

[RichV]

I'm checking the internet daily for anyone selling a 81 #2 body. All the others are out there but not #2. There is an auction on a complete set but I won't bid till near the end of the time period and only if I think it will work out.

[justinc1081]

I have some extra bodies at home for an 80, will check to see if #2 is any good when I get home

[RichV]

Is it okay to mix 80 carbs with 81? I know there are some differences but does it matter? Can you "convert" and 80 to and 81?