Gas Tank Question

[OldDog]

I posted this on the Cruiser forum and got few answers.

I just bought a Vulcan 900 LT. Yeah, I love it so far. Here is the biggest concern I have - the gas tank.

I fill up the tank, go on a two or three hour ride and go to fill it up again. When I release the tank's cap (requires the key), air rushes INTO the tank and the tank actually expands back to its original size. The first time I saw this I thought, "No way!" Then I saw it again. Other forumites have told me that the tank is pressurized (because of the gasoline sloshing around) and that when I remove the cap and am RELEASING pressure. No way. When I remove the cap, I am releasing a vacuum and the tank expands. I have seen this three separate times and it is the same every time. Suction, tank expands. I have over 800 miles on the bike, so I have put a few gallons into it and I see it over and over again.

Isn't there some venting system built into the cap or the tank to prevent this, or is this normal for the Vulcans? Weird problem, I will admit, but I would like an answer just the same.


Little help, please?

[brother]

My Nomad builds up pressure and releases it thru a valve built in the cap which sing like a bird when venting. I dought if it has a vacum unless the vent line is restricted and then it would only be on a FI bike and I still don't think the bike would get the proper fuel flow.

[OldDog]

It is fuel injected.

[QKENUF4U]

def. a venting problem. since its fuel injected the pump is able to keep the fuel supplied to the engine but in turn sucks your tank INWARD/COLLAPSING it till you pop the lid. you need to get the vent cleaned out before ya burn up the pump (its having to work WAY harder) from all the bikes ive worked on you should have a vent "in the cap" or "under the cap"
good luck

[samarnold55]

http://www.gadgetjq.com/whistle_stop.htm

Try Gadget's web page, he has some good information about changing the release valve in the gas cap.

have you noticed it whistling after it sits in the sun a long time too?

[OldDog]

YES! I feel vindicated from everyone else telling me that the tank was building up pressure and not a vacuum. I know what I am seeing.

I will try that in a day or two. Thanks, guys.

[EdAZ]

OldDog,
I have a 900 and mine dosnt do that. It does sound like there is a problem...Ed

[OldDog]

FOLLOWUP:

Dealer is closed on Mondays. Took it in today to see the service manager. He looked (ten feet away) at the tank and went inside to call someone else to come look. They removed the speedo/odo cowling and discovered that there is a vent hose at the right front, top of the tank and the hose curves under the tank and ends up near the center bottom of the frame. It was clogged. They took the front end of the vent hose off and found that the hose itself was not clogged. They looked closely at the "spigot" where the hose clamps on, and it was painted over at the factory. No holes in the paint at all. They took a small piece of wire and "routed out" the painted-over hole and replaced the vent hose.

Then, he showed me where (hidden under the cowling) the tank's paint has already cracked. He ordered a new tank, no questions asked. He is going to report it to the factory so that they will be aware of it and check it during assembly. We went and looked at the 900 Classic and the tank looks entirely different from mine (900 Classic LT)! Of course, the vacuum did that little by little, but he recognized it as soon as he saw it and told me that the tank was "deformed." I am still riding it, but I will get the new tank upon arrival.

Thanks, guys. I am still a noobie at this stuff, but it is great fun learning it all again!

Mike
OldDog

[QKENUF4U]

SWEET DEAL MAN !!! glad to hear ya have a dealer thats not got his head up his A$$.

[OldDog]

I thought I would update this.

The new gas tank came in last week and was installed and the bike returned to me the same day. The shop manager wanted a few pictures as requested by Kawasaki, so I took a few for him that showed the obvious warps. Then, Kawasaki requested that he send them the tank.

As last I heard, the tip end (where the hose attaches) was painted over in the factory and it never did breathe. The fuel pump (inside the tank) kept sucking the tank downward as the gas was used up and permanently warped the metal tank. Now, that's a helluva pump!

The new one was checked carefully at the dealership, even so far as to blowing air into the tank to make sure that is would breathe. I have seen no signs of the old problem. Everything is back to normal. I am a happy camper. I like to give credit where it is due.

[jukief]

You had a good ending to that problem! It's great that you were observant and realized something was wrong. And your dealer did well by you. Glad to hear it all worked out well.

Now you can get used to the Vulcan whistle. I like it; it's music to my ears.