1979 yamaha?

Question

I have a 1979 Yamaha 1100 special.

My first question is, is this a virago? Someone told me it was .

My second question is, On the fuel tank there is two petcocks comming off of the bottom of it (one on each side). And there is two fuel line hookups on both of them so there is 4 in all. And there is 4 carbs. My question is does one gas line go from each of them to a carb. like one for each carb? (there is only the two outside carbs have a gas line running to them. and the two other fuel line hookups are just hooked up to the other side of the gas tank so it goes right back into the gas tank. )

My next question is when i spray a little starting fluid into the two carbs that dont have fuel lines going to them it will fire. It seems like it burns off the starting fluid then dies. Could the gas line problems cause this? If i made it so there was gas going to all 4 carbs do you think it would run?

Thanks in advance

Answer 1

Interesting that a fellow asks a fair & legit question,,,

gets told to go somewhere else to get info,,

Then the respondents proceed to offer a series of guesses.

As if XS11S's fuel delivery sys is not peculiar enough as-is

Oh well

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Your 1100 came in 2 versions.

Standard and Special

The Fuel Petcock systems on the 2 bikes are Different.

Originally,,Your Special has NO Crossover hose.

There's No "3 Lines"

Nor does it have 4 Hoses to the Carbs.

There's not even 4 Fuel Inlets on the carbs.

.........................................

Here's what it DOES have:

4 Basic "Parts" or "Sections"

#1) A Twin Pair of Dual-Outlet 4-Position Manually Operated Petcocks.

--The Valve Positions are

a)OFF

b)ON

c)RESERVE

d)PRIME

NOTE: When engine is NOT running Fuel will Flow TO THE CARBS,,,ONLY when Petcock is in the PRIME position

If You disconnect the Fuel Hoses from the Petcock Outlets,,,,Fuel will flow Directly from the Outlets according to Valve Position

Note:The Outlets are marked with Numbers to assist in connecting the Hoses

--------------------------------------...

#2) A Single Outboard-Mounted,,4-Fuel Port Vacuum-Operated Valve.

The Valve also has a Single Vacuum Port.

The Valve Body consists of a Pair of Fuel Plenums.

1 Inlet Plenum

1 Outlet Plenum

There are 2 INLET Ports Feeding the Inlet Plenum.

And 2 OUTLET Ports Exiting the Outlet Plenum.

NOTE: The Dual Inlet Port Feed TO the Inlet Plenum constitutes the "Fuel Tank Crossover Line"

----------------------------

#3)  Carbs---

Fuel Inlets are "Siamesed"  into "Carb Pairs"---

1 Fuel Inlet serves 2 Carbs.

Carbs #1&2 are paired and #3 & 4 are paired

................................

#4) Fuel Manifold---

This is a Very Simple  " Fuel T-hose fitting" arrangement.

There's one for Each Carb Pair.

It allows the Vacuum Valve to control  the "On / Off" Fuel Flow when  Petcocks are in ON or RESERVE Position,,,,

AND allows the PRIME Position to feed Fuel straight thru To The Carbs---Bypassing the Vacuum Valve at all times,,,,,,and all thru a Single Fuel Hose to EACH Carb Pair.

.........................................

It's complicated enough,,,and rather unusual,,,but it's Not THAT complicated.

Everything needs to be connected Properly of course,,

and you need to understand at a least the basics of the system's Operation so You'll know When ,Where ,How Fuel is supposed to Flow to the carbs

.........................................

Operation is Very Simple,,,not much different than any other bike

OFF,,,is OFF,,nothing happens as far as Fuel Flow

ON  and RESERVE are controlled by the Vacuum Valve.

If Bike is NOT RUNNING,hence NO Vaccum---NO Fuel will Flow.

As Soon as engine produces Vaccum,,,the Valve Opens and carbs then get Fuel

The Idea is that You do not have to manually turn OFF the Fuel each time you park the bike.

You can Leave the Fuel Manually ON "all the time",,,knowing that the Vacuum Valve Automatically  Turns Fuel ON~OF accordingly.

No Forgetting to turn Fuel Off,,or On

.........................................

PRIME delivers fuel Straight Thru to the Carbs.

It BYPASSES the Vacuum Valve's Control over Fuel Flow.

So in effect,,,PRIME works  exactly the same way  as any normal ON~Off Petcock.

It's Intended Use is to "Fast Fill" empty carbs.

For any number of reasons the carbs can become Empty.

When Empty,,,,Turning Petcock to ON will NOT fill the Carbs until the Engine makes Vacuum to open the Vacuum Valve.

Trying to START the Bike with Dry Carbs is almost Impossible because the Vaccum pulses while Cranking it are BRIEF,,SELDOM,and WEAK.

It would take forever to fill the carbs that way,,,so bike would start.

Prime lets fuel go directly to carbs to fill them instantly----just like a normal bike would.

THEN with the Carbs full,,,Bike can start Easily,,,and make enough vacuum to control the valve >fuel flow as-intended.

So the Ritual is:

1)With Dry Carbs,,,Begin with Petcock on PRIME,,,filling the carbs.

2)Start Bike

3)Switch Petcock to ON

At Next Shutdown,,carbs will be Left Filled and Ready for Next Start.

No attention to Petcock is needed.

If Bike is Run Dry on  "ON",,

It MAY need  to use PRIME to Restart,,before Switching to RESERVE.

If bike is left Sitting  several Days,,,Fuel will Evaporate ,,,

and  PRIME may be Needed to RE-FILL the Carbs.

Same applys if Carbs are Drained for whatever reason.

If Bike falls over,,,and the Carbs drain----it will need Prime to Re-fill the carbs.

.........................................

Connecting all this stuff correctly.

First,,lemme say there's "CORRECTLY".......

Then there's a Hack to Bypass the Vacuum Valve "Permanently" which  makes it all work same as a Standard,Normal Petcock.

There's a Couple of options.

But they are ALL easily Reversible.

Reason it's important to know the Fuel Line Connection Hacks is because of  in the event of Vaccum Valve Failure.

***The #1,Primary ,Emergency Procedure is to simply use the PRIME position.

Remember PRIME acts like a Normal Petcock's ON position.

If You are out riding and Vac Valve fails and fuel quits Flowing cuz Vac Valve wont open,,,it's a handy thing to remeber.

Just Use "OFF" and PRIME,,,same as any bike.

Be aware that when on PRIME,,,there's NO RESERVE position to go to.

If ya Dont Wanna fiz a failed Vac Valve,,cant find one,,etc

One hack is to Reverse the Fuel Hoses on the Petcock.

Then,,,the ON & Reserve Petcock Outlet will feed the PRIME Line,,which goes Directly to the Carb---bypassing the Vac Valve.

.........................................

Here's a Picture from Yamaha Parts Book to see the Seating Arrangement of all the worms in the can.....Aaa,,It's not that bad.

You can see how all the hoses go

http://parts.yamaha-motor.com/partimage....

Hover your on lower r/h corner of image and a Zoom button will appear.

.....................

Ok ,,Note the Petcock outlets  have a Front & Rear layout

Hoses # 21  & 22 are long,straight hoses.

Those are the  ON & Reserve Hose.

They connect to "Rear" Petcock outlet.

And Other end is connected to LOWER Inlet pair on the Vacuum Valve(#15)

........................

The "FRONT" Petcock Outlet is the PRIME Outlet.

It's the Hose with the "T" Fittings

We'll just discuss One Side,,,Other side is SAME,,it just looks different  ,because of Hose Lenghts variations to accomodate  physical mounting.

Fuel Hose 23 connect to Front  Petcock Outlet.

There's a T in downstream end of that hose.

One port of the T has a Hose which goes to Carb.

That Delivers PRIME Position Fuel From the Petcock to the Carb

The 3rd Port on the T is connected to Vacuum Valve OUTLET.

Fuel Exits the VacValve >Into that hose>>>into the T....and from the T to the Carb.

So Fuel flows From VacValve and petcock sorta "head on" at each other  TO the "T",,,then is diverted at the T on to the Carb's inlet.

When flowing from Petcock,,,VacValve is Closed.

And vice-versa,,,when flowing from Vac Valve,,,Petcock is Closed

.........................................

Cranking will let a Tiny amount of gas into carbs.

Very,Very Slow Fill rate.

So checking for Fuel via Carb Drain  will APPEAR to show that Carb Does Have Gas.

Actually it Does,,,,but maybe only a Teaspoon full?

When it Needs over 1/2 a Cup in the carb to start & run.

Get all your hoses connected properly.

LOTS easier than I've made it sound.

You can test the Vac Valve by sucking on the Vacuum Line to the Valve.

Any suction should allow fuel to flow at the Carb Inlet Hose

Or,,,just switch it on PRIME ,,and fuel sould flow AT the carb's Fuel Inlet hose.

Then You can go from there & continue w/ your troubleshooting.

Sorry this has all been so long winded.

But This particular fuel system can Trick you into thinking you have plenty Gas in the Carbs,,,when there may be Too Little or even None.

Not Unusual to have a Crossed Hose which deadends and goes "nowhere".

Or an Inoperative Vac Valve.

Occasionally  we'll see a Fuel Line connected to Vacum Port on the Manifold.

Thats Bad News,,,it's a direct Fill into engine

Good luck with it

Answer 2

the bottoms of your carbs have drain nuts open them and see if you have fuel coming out of all four my 81 gsx 750 has a single petlock with 2 lines coming off both go down to pipes connected to the carbs your tank need the equalizing lines and most likely the 2 carbs on either side are connected and fill off of the one line on either side check by opening the drain plugs on all 4 carbs slowly with the fuel petlock in the PRI position they will pour fuel out so don't do this on your grass and let it dry before starting it then move your petlock to on which should stop the flow of gas spray b12 carb cleaner in the bowls through the drain plugs to rinse them out before closing them back up

Answer 3

While I do not know any specific model info about your bike, I do know there should be fuel going to every carb on the bike.  If you have four carbs you will have one for every cylinder and with two of them not hooked up to fuel your bike can only be running on two cylinders at this time, if the bike starts at all.  You should hook those carbs up asap and then sync the four carbs and you bike will be running the way it should.  Check back here or on one the the forum mentioned by the above posters if the bike is still giving you problems.

Answer 4

Not a Virago, You have 3 fuel lines under tank two goto carbs the other goes to other side of tank to equalize the fuel in the tank, Because of the shape of the tank fuel tends to get trapped on either side.  Your bike may need the carbs torn apart and cleaned well and possibly rebuilt. The fuel petcock (valve) may need rebuilt also.

Answer 5

First,you have to be sure of what model your Yamaha is.

Second,join an online motorcycle group,like I did last month when I got my motorcycle.My group is model-specific,and I am sure there is a group out there for Yamaha motorcycles.

I have learned a whole ton of stuff using my group.

Try it! Good luck,and be careful!!!

Answer 6

It is NOT a Virago. The Virago is a V Twin, the 1100 Special is an inline 4. There are some decent forums on the NET for the Old Yamaha 850/100 Specials and there are a surprising number of them still around. Good Luck with it.

Answer 7

IDK!@#$<3