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Discussion Starter #1
I have an 04 St4s. It has always hissed when I opened the tank. I rode it this fall and it must have got very hot. When I opened the tank it swelled and sprayed gas at me. I have taken the tank and tried to find out what is not venting. I have taken the nipple off inside the cap and it is open and not clogged.

I tipped the tank forward to look at the lines underneath and there are a couple. One I assume is the normal vent which drains out the bottom. When I rotated the tank back down some gas came out of the line. So I assume that one is clear.

There are 2 other line I believe. Can anyone tell me what the other lines are and what else to check?

Also I think the tank may have swelled as it does not sit on the frame against the rubber guard things on the bottom of the tank. Any suggestions how I can get this tank back to normal?
 

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STOP! Do not ride the bike. Take it to dealer or speak to someone that knows this problem. This happened to me and the tank began to squash itself. A $2300 problem. It's part of the emission control system clogging. Look at the sides of your tank. Are they distorted?
 

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dammit, I have this problem as well.

by emissions control system do you mean the charcoal canister system? should be pretty easy to eliminate, no?
 

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My ST4 was doing this too, honking on shut down. When i had the tank off for cleaning and re-lining i looked at the cap the tapered part with the rubber seal on top was very hard to move a few squirts of WD-40 and moving it back and forth seems to have freed it up and I've not gotten the honk or hiss since then but its only been 3 tanks of gas so far.
My canister is gone i have two vent lines that seemingly do nothing but run from top of the tank under the gas cap to the vent drain under the battery.
 

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There are two "vent" lines, one equalizes the pressure from inside the tank and this is the one that's probably blocked, the other is just a drain from gas at the flap. An easy way to check is to lift the tank, follow the lines and blow in the two that either open at your right footpeg or end at the canister. Blow in both of these and make sure they're not blocked.
Check this out: http://www.ducati.ms/forums/92-hypermotard/88653-removing-evaporative-emissions-canister.html
 

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Yes. Jduke is correct. I left the canister in place i case of future regulations but it is blocked off and vented correctly now. Never had a problem since. Also fortunately for me since this was emission control system, it was covered under the 7 year warranty. So Ducati bought me a new tank.
 

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Discussion Starter #7
There are two "vent" lines, one equalizes the pressure from inside the tank and this is the one that's probably blocked, the other is just a drain from gas at the flap. An easy way to check is to lift the tank, follow the lines and blow in the two that either open at your right footpeg or end at the canister. Blow in both of these and make sure they're not blocked.
Check this out: http://www.ducati.ms/forums/92-hypermotard/88653-removing-evaporative-emissions-canister.html
I read the post quoted and it doesn't appear he does anything to the line coming from the tank. I can see mine looks like it is being crimped between the head. If I remove the other hoses is there a need to do anything with the hose from the tank?
 

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Mr Leakered
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If gas came out one of your lines and the tank was about half full or less then that one is your trouble. It is/was pinched. When you lower the tank, always check that the two lines are free by wiggling them.

The other option is to Y them together. You'll see this in the Duc Service Manual.

Also, the emissions canister is known to cause problems. Something like, once it is fill with fuel, it is very hard to get it vented. Sort of vapor locked?

If you look at it, there is an overflow like on the CANISTER. Therefore, it is not a closed system like the automotive equivalent. Therefore, it is essentially dead weight and a problem.

Folks in Kalifornia pull these all the time and don't have problems with the Man.

One the third line, it comes from the airbox drain. Either make sure it is not cooked by the header pipe, or like me, seal it up. I never find enough of anything in the airbox to worry about with it blocked off.

Have a good one.
 

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hose from the bottom of the tank just needs to somewhere that is safe should vapor or liquid gas drip out of it and needs to be able to flow without restriction.
point is somewhere off to the side so if it puks on a ride it "should" miss the rear tire.
Mines goes down and follows the battery vent tube under the right foot peg
 

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Discussion Starter #10
I will try to remove the canister lines and then try to get the tank to sit back on the frame properly. If I can't, anyone know where I can get a new tank in senna grey for a good price?
 

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I will try to remove the canister lines and then try to get the tank to sit back on the frame properly. If I can't, anyone know where I can get a new tank in senna grey for a good price?
Hope you can get it back in shape but I have an extra tank if you can't. However it is red. Might check Ebay also.
 

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Discussion Starter #12
It seems the top and bottom have swelled more than the sides. I'm going to tap on the bottom with a rubber mallet and maybe put a come along around it with a towel under it and see if I can bring in the sides in a bit. I'm just hoping I can get it to vent properly. I can't imagine how many hours of labor this would be at a shop.
 

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Mr Leakered
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Since positive pressure expanded it, maybe some very careful use of vacuum pressure could bring it back into shape? Of course, that could go very wrong also.

Have a good one.
 

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Discussion Starter #15
Since positive pressure expanded it, maybe some very careful use of vacuum pressure could bring it back into shape? Of course, that could go very wrong also.

Have a good one.
I thought about that but haven't come up with an idea of how. I thought about a toilet plunger over the filler hole but.......
 

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Mr Leakered
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You could use a Mity vac brake bleeder pump. It might take a while, but you would have good control of the amount of vacuum. If you use any kind of mechanical device, I think that you'll want to have some way of dumping the vacuum very quickly if you need to.

I don't think a shop vac has enough vacuum to do it and it would be moving a lot of air.

Have a good one.
 

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You'll want to remove the fuel pump assembly before pulling a vacuum on the tank.

Mighty vac might do it but thats allot of pumping. Got a friend who uses a air brush? most air brush compressors also have a vacuum port. I use one for brake bleeding with a jar.
 

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I don't think there is a way to achieve an exact reverse of the forces that led to the tank distortion. I mean, worth a try but as previously mentioned pull the internal plumbing. I've heard of filling the tank with water and freezing it gets some results but sounds like you had expansion rather than contraction. Which opposite of what occurred on mine.
 

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Mr Leakered
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I agree that is it a risk from any perspective. It could collapse or contract at some place other than where it expanded. Or, it could start leaking. That said, positive pressure and a vacuum are equal and opposite. The hope would be that the material would yield at the same locations. Although, compressive yield and tension yield stresses are different values. Also one represents failure while the tension can still go to ultimate values.

Have a good one.
 

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Discussion Starter #20
I have removed the canister and hoses and ran and rerouted the line that used to go to the canister to run to the bottom of the bike. Is this all I need to do with that hose?

Where can I get some caps to go over the nipples on the intake that the hoses used to run into? What's everyone else using?

As far as the tank after I moved the hose it sat closer to the frame. I tapped it some with a mallet and found a small ripple underneath that I tapped a few times and it fits closer than it has since this happened. I think it swelled more on the right side because it is sitting just off the frame whereas the other side is right in the frame as it should be. Unless someone was looking for it I don't think they would notice. I put 1/2 a tank in it and it seems to be holding fuel so I think I'm ready to put it all back together.
 
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