Fuel tank ..and hoses!

[Jim __]

Please correct me if I'm wrong.  I thought non-cal fuel tanks had only 1 nipple.  It did not vent the tank.  It was the drain line for anything that might get into the well surrounding the fuel cap.

[RFH87_Connie]

Please correct me if I'm wrong.  I thought non-cal fuel tanks had only 1 nipple.  It did not vent the tank.  It was the drain line for anything that might get into the well surrounding the fuel cap.

That would be correct.  The cap does the venting - it is only supposed to let air in so fuel can go to the carbs.  Oneway diaphram construction.  Under heat pressure, air does escape from the cap giving the bike the "singing" when she is parked.  As far as I know, the drain line is the nipple slightly to the right side of center on the rear of the tank.  You should be able to blow into it and feel air at the gas cap.  The vent line I believe goes down the right side of the engine to exit at the swing arm (below by a few inches).

Follow this advice from T-Cro (if not all of it):

You need one line coming from the gas cap drain nipple on the back of the tank going down to the swing arm area.
Plug the remaining two nipples on the back of the fuel tank.

[Jim __]

Jet86,
If you remove the o-ring/grommet from the fuel tank cap ring (see attached doc from previous post), you've essentially set up your tank as a 49-state version (and you'll get to hear it sing).  You can then cap the far right nipple.  The center nipple is the overflow/spill well drain and should go just behind the trans so it can discharge to the ground.  Absolutely cap the far left nipple, tightly!

[T Cro ®]

Jet86,
If you remove the o-ring/grommet from the fuel tank cap ring (see attached doc from previous post), you've essentially set up your tank as a 49-state version (and you'll get to hear it sing).  You can then cap the far right nipple.  The center nipple is the overflow/spill well drain and should go just behind the trans so it can discharge to the ground.  Absolutely cap the far left nipple, tightly!

Actually all caps are the same no matter if 49er or CA model.... All gas caps let air in but not out; this "can" cause pressure when heated and thus the tea kettle like sounds as well as near flooding like behavior. I long ago removed the little orange stopper looking piece inside my fuel cap, don't remember if I removed anything else though. Some folks complain of fuel smell while riding after doing this "mod" myself I've noticed or cared.....

[Jim __]

Yes, the caps are the same but the cap vent nipple, where the air vents to atmosphere, seats into a grommet in the cap ring when the cap is closed on the cal tanks.  Capping the nipple at the rear of the tank, with that grommet in place, will seal the tank.

[T Cro ®]

Yes, the caps are the same but the cap vent nipple, where the air vents to atmosphere, seats into a grommet in the cap ring when the cap is closed on the cal tanks.  Capping the nipple at the rear of the tank, with that grommet in place, will seal the tank.

Got ya... Never gave it too much thought as to what other function the spillage drain might perform as I simply blew air through the nipple first time around to discover where it went. For some reason I was under the impression that the vent worked through the keyhole itself as there have been a few riders that developed venting issues from a tightly fitted tank bag; but they may have also had a drain hose issue too.....

[RFH87_Connie]

Purely hypothisizing here because i haven't actually seen one.  I think ALL of the caps have the standard oneway vent and were built the same.  In addition, the bikes sold or sent to CA for sale as "new" had an additional grommet of some sorts pushed in or suck inside the underside of the gas cap.  I'm sure in someway this "sealed" the venting of the cap and caused the canister to take the vapor pressure instead of the atmostsphere.

And yes, I had mine apart to rekey it.  They vent right up thru the key hole.  A little red seal and a bunch of channels for the vapors.

[Jet86]

now i'm a little confused, this is how i have it set up, i got some rubber caps from autozone and caped 3 carb nipple only leaving the 1 line for the petcock vacuum, then i caped the 2 nipples on the tank leaving the fare right line in place so if i over fill it with gas it will run to the ground and not all over the top of my tank.

the bike is running ok so fare.

PS. when i opened the tank cap i did see this little metal round pointy nipple that seals the drain hose once the cap is closed, i did not try to remove it.

[RFH87_Connie]

According to the diagram I attached above from the manual, the more central hose (and slightly to the right) is the "water drain".  I think the other hose nipples have an OEM colored stripe or tape on them (sometimes)?  You may have blocked the wrong one.  Perhaps the one you are using is the vapor return hose from the canister and comes into the tank neck up at the cap also and is working OK.  Again, just guessing on the vapor line.

[Jet86]

tomorrow i will look at the gas cap again but i dont remember seeing any other hoses under the gas cap.

[RFH87_Connie]

It may actually exit into the tank just under and inside the fill neck.  It would be somewhere within the sealed (pressure) area of the gas tank, most likely just inside the gas cap but below the filler neck rim.  It might be something you can't really "see".  It could just be a slot or something (pin hole)as only vapors are supposed to go thru - not fuel.  I have a CA parts bike in my shed but can't get to at the moment.  Interesting.

[Jim __]

RFH87, you are correct.  The center nipple is the water drain from the well where the cap seats. 

JET86, get a hose, connect to the center nipple and blow through it with your fuel cap closed.  You will hear air escaping from around the cap.  That's good.  Run that line to the ground.  Put the hose on the far right nipple and blow into it with the cap closed.  You will feel resistance but still be able to blow into it.  I don't remember feeling any air escaping from the cap key hole on mine but your will hear air inside the tank.    This is the nipple to leave uncapped if you are not going to remove the grommet which seals the pointy nipple on the cap.  Open the cap and connect your hose to the pointy nipple on the cap and blow again.  You feel/hear air from the holes on the bottom of the cap.  The left nipple should be capped.  If you blow into it you will hear the air escaping into the tank, somewhere.  This is the fuel return line for the pump you removed.
[/quote]

[Jet86]

So the middle nipple at end of tank is the fuel overflow correct? and the fare right nipple is for anything else like water/fuel.

right now i have a hose on both nipples run to the ground and capped the fare left nipple.

pics

is that little slit inside the tank the fuel overflow?/ center nipple?'  i did use the hose and blew threw each nipple but could only feel air coming out where the pointy thing seats into. but i did hear the air inside the tank like you said.

[MAN OF BLUES]

looking down at the rear of the tank;
The left hand hose is the fuel return hose, it has a red dot or tape on it, and was connected to the liquid / vapor separator down low.
The middle hose is the Water drain hose, no tape color on it, it runs down and back alongside the coolant overflow hose, and terminates at the rear axle. It drains water that accumulates in the cap area OUTSIDE of the cap to tank seal gasket.
The right hand hose is a tank breather hose, which runs from that grommeted nipple inside the cap, down to the liquid / vapor separator. it has a blue tape/ dot.

leave the middle hose attached, and running down to the axle to drain water.
connect the left and right hand hoses with a short piece of the appropriate size hose.

[Jim __]

MAN OF BLUES,
Since the Cal version tank gas cap is sealed by the grommet the cap nipple sticks into, won't connecting the return (Red) and vent (blue) together effectively seal the tank?  It sounds like neither his or my gas caps vent to the atmosphere through the key hole.

[MAN OF BLUES]

yes
this is why I said to run a hose between them.
My 86 was a cali bike. this was what I did, as I didn't like having plugs installed, the rubber breaks down faster than the hose does.

if you ever decide to disassemble a cap, you will find that the shroud the latch lives in is vented thru that nipple, which in turn used to connect to the vapor thing you removed. Connecting that line right back into the one on the left, just makes a "closed circuit".

none of the tanks have any venting thru the keyhole. that area is completely sealed.

[Jim __]

Ok.  Now I'm confused.  So if it's a closed circuit, when the gas leaves the tank through the petcock, how do you prevent a vacuum from building in the tank?  Or, is there a vent to atmosphere I'm missing?

[MAN OF BLUES]

RELAX... STOP ANALYZING...
 

RESPONSE #23

http://www.zggtr.org/index.php?topic=15181.msg205724#msg205724

There is a one way valve with an opening  to atmosphere in the cap shroud.

[Jim __]

Thanks for reeling me in.  I'm sure there's a pill I could take for that.

[RFH87_Connie]

These are not my pictures.  I think maybe SIG or someone else was doing a re-keying and took some pretty good pictures.  There are 15 pictures in all - if you want all of them, shoot me an email to send them to.  The orange "thing" is the oneway valve/flapper if I recall correctly.  You can also trace the channels out to hopefully give you a better idea of what is going on inside the gas cap relating to venting.  There's a lot going on in there.

Thanks MOB for clarifying some of my assumptions.  Hopefully I didn't create more confusion with pictures.