Gas Tank Games

[Lex]

For some of you this maybe old news but in the hopes of preventing any other newbies from learning the same thing the hard way here is my report.

 

I started a small project on my ’01 V11 Sport today. One stage of the project involved lifting the back of the tank slightly to run some wires. Even counting fabricating a small bracket I figured less than an hour. Boy, was I wrong. Six hours later, I was cleaning up. What took so long? The tank would not go back on the bike. I pushed, pulled, lubricated the mounts, checked for something in the way, no help. Finally, I took the tank off completely; I found the front of the tank was rubbing on the frame but no clue as to the problem. I’ll skip all the things I tried but nothing helped until I pulled the vent tube that used to run to the “pollution cans” under the seat. The tank made sucking sound and grew before my eyes! The tank then dropped into place just as it has every other time I’ve messed with it. Obviously, the tank had contracted due to a good deal of vacuum.

 

I’ll open (and close) the gas cap before I move the tank in the future and make it a habit to park the bike with the tank nearly full, fuel doesn’t expand and contract nearly as much as air. This can’t be good for the tank (or its paint!) any suggestions for eliminating the problem without dumping raw gas on the ground?

 

Still amazed by watching my tank grow,

 

Lex

[al_roethlisberger]

Yep,

 

Congratulations, you've unfortunately just met the infamous "tank suck" condition many V11 Sport/LeMans owners have dealt with since the introduction of the V11 Sport in 2000

 

As you have discovered, the quick fix, that is, to return the tank to normal proportions.... is to open the cap or disconnect the emissions hoses, which of course allows the tank to equalize and pop back out.

 

But the real issue is in your tip-over valve. For emissions equipped bikes these days, the cap no longer vents to the atmosphere as they used to. Instead, intake vaccuum is used to "suck" the gasoline vapors from the tank into a charcoal recovery system, which is then fed back into the intake for clean burning. Additionally, your overflow hose has a one way valve, called a tip-over valve.

 

If this valve get oriented "non vertically" it seals off, not allowing the tank to breath. Because this hose and valve typically hang free, if the hose is moved and orients the valve incorrectly, the tank will seal... and contraction of the internal fumes and/or vaccuum from the intake will cause the "tank suck" condition.

 

Fortunately, it's an easy fix... just attach the tip-over valve to a vertical member of the frame or other mostly secure item under the tank with a nylon wire-tie, and all will be fine. Or like some folks, you can simply remove the valve altogether. The disadvantage there of course is if the bike falls over, without the valve, you may dump fuel on the motor and ground, which can be a "bad thing"

 

Hope that helps, and welcome to the Forum

 

al

[Lex]

AL,

 

Thanks, I didn't realize the valve was position sensitive. I'll orient it

properly today.

 

BTW, I'm not that new to the forum but I have been a lurker for the most

part. I didn't have anything interesting enough to say to make a post.

Watching my tank grow was interesting to say the least.

 

Cheers,

 

Lex

[Guest Ragin' Pit Bull]

The best thing to do is have the dealer remove all that crap before you even take delivery, unless of course, you're in Kalifornia.

[al_roethlisberger]

..yes, if possible. But a lot of dealers won't do that.... warrantee reasons, blah-blah-blah

 

But it is trivial to be sure. You can do it in 15 minutes if just hacking around, or "do it right" nice and neat in about an hour.

 

However, keep in mind that the main issue with "tank suck" is related more to the tip-over valve than the emissions/cannister setup. So one could remove all of the emissions, but still have your tip-over valve oriented incorrectly and have this problem if you just capped off the vacuum nipple that had been going to the cannisters and had a pressure differential.

 

So, two things... make sure that valve is verticle, that is, if you keep it. Debatable, but think it has value as this is overflow around the cap, not venting. And second, don't cap off the vent/drain line that went to the cannisters, just lash it to somethig like your oil line and let it drain under the bike in case of overflow, and to allow venting.

 

Or yes, as Victor points out... you can just take it ALL off(although you should still extend the vent/overflow lines down below the bike to avoid fire hazards) Your choice.

 

al

[jrt]

So, who's gonna show lex the 'secret handshake'?

 

Welcome to the club.

 

 

I just removed the rubber grommet under the tank cap- that works just fine, and no- I've never leaked gas- no matter how full I got the tank.

 

cheers,

Jason

[dlaing]

I cut a notch in that little rubber grommet nib under the gas cap, no more suck!

I even crashed tested it and left no gas on the asphalt.

However, repositioning the tip over valve is the better solution for safety and potentionally for a cleaner environment!

EDIT May 2006, someone on the forum nearly got flambayed. I highly recommend the repositioning method, rather than removing anything

[Lex]

Addendum

 

All,

 

First, thanks for the help. I not as new as some think (a couple of months) but I am new and good advice from nice folks makes me even more sure I will look back on the purchase of my first Goose as a good move. I originally wrote a small “how-to” based on what I learned during this experience but Al’s write-up in the FAQ (the FAQ is a great idea, BTW) covered everything I was going to say and more. Below are a few comments.

 

First, I had already removed the charcoal canisters, not because they hurt the engine in any way but because it drove me crazy (I’m an old fashioned, anal retentive, engineering, BMW riding type) to give up the tool kit space. I didn’t, as nearly as I can tell, change anything from the disk shaped valve “up” toward the tank. FWIW, I would love to figure out a way to mount the canisters W/O giving up the under seat space, any ideas?

 

For my fellow newbies, there are two valves in the line we are talking about; the one closer to the tank is the “tip-over” valve. It is (at least on my bike) black and basically cylindrical. You can test it by sucking or blowing into the top; air should flow freely while the valve is vertical. As you tilt the valve you will find it stops flowing air at a certain point. Please note that the valve and lines may be full of gas fumes, getting that in your lungs is probably not the healthiest thing you can do. The second valve (black and dirty yellow on my bike) is disk shaped and doesn’t seem to cause any problems.

 

I did some testing and found my bike would not vent the tank while on the side stand. It worked fine on the shop stand. What I discovered is that the valve is tilted (the top is to the left of the bottom) by the way Guzzi “plumbed” it into the system. Put the bike on the side-stand and it leans to the left. The valve on my bike was then tilted enough to stop the flow of air in and out of the tank. I solved the problem with a solution similar to what Al mentioned, I attached the valve to the frame and added a longer hose to connect the valve to the tank. Since I didn’t change the location of the tip-over valve I would say this problem could affect any V11, if your tank makes “whooshing” sound when you open the gas cap check the valve.

 

Finally, I couldn’t get Al’s links to work* and I failed to find the article using the search function (both before I wrote and a few minutes ago) but you can read the thread I think he is linking he calls “Tank Suck” by going to page six of the “Technical Topics” forum, it is near the bottom of the page.

 

Cheers,

 

Lex

 

*I get bumped back to the login screen

[dlaing]

There are a few places that MIGHT fit the evaporation cannisters.

1) mounted visibly behind the muffler hangers.

2) Under the gas tank

3) eliminate your crossover and put the cans where the crossover was, or better yet, put the battery where the crossover was, and put the tools where the battery was. Or put the battery between the engine and the front tire, which would balance the bikes weight nicely.

4) Perhaps there is enough room by the rear shock absorber.

5) Eliminate your airbox to allow more space under the tank.

6) Visibly under the jugs. Or build a lower fairing to hide the cans under the jugs....

 

Sorry most of the ideas are lousy.

I have been wanting to put my cans back on, but there really is not much space available.

I was wondering what the reason is for two cans. Perhaps one can would be sufficient.

Would having only one can, restrict flow?

Or did they install two cans because the capacity to reduce emmisions is less with only one can?

My guess is that there would NOT be a flow problem with one can, and that the emissions would only be slightly higher.(Not twice as high)

[al_roethlisberger]

Also, keep in mind that the pre-2002? ....maybe pre-2001? ...bikes have the evaporative cannisters under the seat where the tool-kit goes. But all 2002 and new bikes have the cannisters mounted behind the exhaust crossover right in front of the rear tire.

 

While you do get the tool-pack space back, I just thought it looked awful, and as you pointed out Lex... I too was fairly anal-retentive and wanted to do without all the various extra hoses the setup presented

 

...so it came off the same day I brought the bike home.

 

al

[Guest gooseorduck]

This is good info, mine is an 04 and I have the same problem. I'll take off the tank this weekend and check the orientation of the tip over valve.