Fuel Leak Description

[ucdyamaha]

Ok, I really appreciate the assistance with the electrical trouble. All electrical systems are currently great. Here is a picture of the new trouble: fuel leaking out of a black hose hooked up to a black box (air cleaner?)

It seems that when the petcock is flipped to reserve this outflow of fuel stops but I haven't confirmed this.



I also have an online movie showing it, but my voice is muffled.
Movie showing hose

Here is a rough transcript of what I was talking about:
"So this is a summary of my fuel leak problem: This black hose here had fuel leaking out of it uh even when the bike was off, this is a black uh device I'm not sure what it is but it must be an air cleaner and here's the carburetor and here's the fuel petcock. In any case this hose was leaking from about the middle near the center stand location"

So in summary: Hot day, black hose leading to black box, fuel flowing--Can't be good !!!



This last picture is from the top direction showing how the black hose is connected to the air filter (or at least thats what I think it is...)

[ratbyk]

Fuel Leak

On my bike the hose in question comes off the left rear corner of the fuel tank. There it plugs into a tube approximately a 1/4" in diameter. This tube runs up through the tank and ends up at the left rear corner of the filler cap recess. It's purpose is to allow excess fuel that has spilled during fill up an escape route.
If you have over filled the tank or almost filled it to the top and parked in the sun, then the expanding fuel will bubble out of the fuel cap vent and spill into the cap recess. Next stop, a puddle under the bike. It is supposed to work this way. Do not overfill the tank!
Ken/Sooke
78E Ratbyk
82 FT500 "lilRart"

[MartyA]

I think Ken's correct. It looks like an overflow tube. Anything that small and that shape on the XS is either a vacuum line or a vent line.

[MartyA]

Eric, see if you can get a Clymers or Hanes repair manual. They are a great resource.

[ucdyamaha]

Thanks a bunch

It seems that ratbyk is right on, and I overfilled it. After some more riding, I haven't noticed anymore "leaking", and the leaking did seem to correspond to the tank venting excess heat/fumes. That would make sense. The hose however, must bypass or connect to the air cleaner, because it sure does seem to come out of that "black box" !

I will use Amazon I suppose and pick up a 850 book.

Any ideas on how to tell which model I have?

[ratbyk]

Model Identification

To determine which model that you have, copy down the VIN number, (chassis serial number). It is located on the left side of the steering head stock, a reflective piece of tape with manufacturing date etc. Compare it to the chart below. That should tell you exactly what model that you have.

Serial Number & Model Identification
US Models:

Year
Model
Serial #
Color(s)

1978 XS1100E 2H7-000101 Macho Maroon
1979 XS1100F 2H7-020101 Magenta Red, Indigo Blue
1979 XS1100SF 3H3-000101 Carmine Red, Black Gold
1980 XS1100G 3H5-000101 Diamond Silver, New Ruby Red
1980 XS1100SG 3J6-000101 Black Red, New Ruby Red
1980 XS1100LG 4H3-000101 New Yamaha Black
1981 XS1100H 4R1-000101 Indigo Blue
1981 XS1100SH 4R0-000101 Black Blue, Cardinal Red
1981 XS1100LH 4W1-000001 New Yamaha Black
1982
XJ1100J
10M-000101
New Yamaha Black, New Ruby Red



Non-US Models:

Year
Model
Serial #
Color(s)
Countries

1978
XS1100 2H9-000101 Macho Maroon Europe
1978
XS1100E 2H8-000101 Macho Maroon

1978
XS1100E 2H9-100101 Macho Maroon Oceania
1979
XS1100 2H9-020101 New Pearl White Europe
1979
XS1100F 2H7-110101 Indigo Blue, Magenta Red Canada
1979
XS1100F 2H9-110101 Magenta Red Oceania
1979
XS1100SF 3H4-000101 Black Gold, Carmine Red Canada
1980
XS1100G 2H9-130101 Diamond Silver, New Ruby Red Europe
1980
XS1100G 3U7-000101 Diamond Silver Canada
1980
XS1100G 3X1-000101 Diamond Silver Oceania
1980
XS1100P 4H9-000001 White Others
1980
XS1100SG 3U9-000101 Black Red, New Ruby Red Canada
1981
XS1100H 3X0 New Yamaha Black Europe
1981
XS1100H 3X1-003101 Black Red Oceania
1981
XS1100H 4T1-000101 Indigo Blue Canada
1981
XS1100LH 4W2-000001 New Yamaha Black Canada
1981
XS1100RH 5N5-000101 New Yamaha Black Oceania
1981
XS1100S 5K7-010101 New Yamaha Black Europe
1981
XS1100SH 4T0-000101 Blue Black, Cardinal Red Canada
1982
XJ1100J 11G-000101 New Yamaha Black, New Ruby Red Canada
1982
XS1100 2H9-140101 New Yamaha Black Europe
1982
XS1100 Police 5H4-000101 New Yamaha Black, White Oceania
1983
XJ1100K 11G-010101 Sparkle Red Canada
1984
XJ1100ML 11G-100101 Blue Black Canada


Ken/Sooke
78E Ratbyk
82 FT500 "lilRat"

[ucdyamaha]

Not Overfill

That hose just keeps leaking !@!

It is like a siphon, pulling all the fuel from the tank. I only put a couple of gallons in to begin with, so the overfill theory seemed strange, but I wonder what could cause the tank to just spew fuel like that. I just ran out of gas for the second time, and this is getting old quickly.

I wonder if this is related to the Carb. floats at all. The bikes sound and reponse behaves rather irradically, not a linear acceleration like I would expect.

[ucdyamaha]

oh and this is a XS850 by the way

Thanks for the model info but this particular bike is an XS850 a member of the: Yamaha Triples

[John]

The overflow pipe is routed through the fuel tank, and chances are it is broken/rusted through inside the tank. That would explain the constant draining. A quick check would to be blow some very low pressure air through the hose, back to the tank, and with the cap open, listen for bubbles or air escaping inside the tank. Even plug the drain hole at the filler neck while blowing into the hose. The loose end of the hose should drain near the back of the engine, not not too close to the exhaust cross over pipe.

[ratbyk]

Fuel Leak

I did not realize that this problem is on an XS850. Not familiar with them. Would assume that this still runs off the back of the tank and is an overflow drain.
You had better trace it back to it's source and confirm where it originates. If it is like the XS11 and is an over flow tube/vent that is rusted out within the tank you could plug it with something like a golf "T". After that make sure that you do not overfill the tank.
Ken/Sooke
78E Ratbyk
82 FT500 "lilRat"

[ucdyamaha]

This URL below is pretty good at breaking down the fuel leak scenarios:


Another Set of Explanations regarding fuel leaks in general

I need to get a good understanding of what is going on in a carburetor when it is operational and when it is leaking. I think the black tube is a carb. overflow tube.

My plan of attack:

1) When able, remove the tank, plug/pinch hoses to prevent fuel drain.
2) Inspect the tank searching for rusted holes
3) Possibly remove carburetors when I've learned enough
4) Disassemble and document the Carburetors
5) Identify if a "float" is ""stuck""

[desert1]

model identification

My 79 special I bought as a parts bike last fall carries the serial # 3h4 with the manufacture date Nov. of 78, the color is carmone red and the decals say special, the engine and frame #s match, I believe its a 79 Special since it was built in 78 I suppose you could call it a 78 Special. Anyone else out there have a bike with the prefix ID 3H4?
Bruce
78XS1100 Alpha
79XS1100 Special

[CMA1]

Yeah Bruce,
Mines a 3H4.... Nov'78 as well.Does that mean mine is a "parts bike"??? guess I shouldn't joke eh? she'll hear me typing...
Larry

[ucdyamaha]

Fuel Drip Slowly from Airbox

Well I have a suspicion that my ignorance of petcocks is to blame for the overfill tube leak. I did have the petcock left on Prime instead of the On position. This was set to PRIME at various times when it shouldn't have been, and this could account for the big fuel gush.

On the 1980 XS850, there are 3 cryptic petcock settings, ON, RES, PRIM but no OFF !! (Which would have been useful for taking off the tank without spilling fuel) But in any case, the fuel is not leaking excessively anymore, but has slowed to a drip from the black air box.

I took it to Davis Motorsports here in town and Jeff told me it should get 35 miles to the gallon baring this fuel leak. I'm inclined to believe him, and my next step will be to pay about $30 bucks per carb for a rework kit that he can purchase.

I just took the M1 test here in Woodland, CA It wasn't as bad as I had feared, but I did practice a lot to get that big 850 around the circle !!