HyperMotard gas tank leaking

[number9]

After replacing the fuel filter and the thermistor for the low-fuel light, and installing a new o-ring for the flange that attaches the fuel pump to the bottom of the tank, I've got a new problem. Specifically, a fuel leak. When the bike is being stored.

The strange thing is that if I run the bike for 5-10 minutes, there is no leak. But if I shut it off, and wait 15 minutes or so, it will start to leak. On this model Ducati, there is a large plastic cover that protects the quick-release fuel line connectors. With the flange cover on, you can't really tell where the leak is coming from. So I took the cover off to investigate. The first thing that I noticed was that one of the bolt bushings for the cover has become elongated, and is no longer flush with the rest of the cover:



The flange is attached to the tank with 6 (I think) bolts. 3 of them attach the flange to the tank directly, and the other 3 attach the cover to the tank and go through the flange. In other words, the cover being attached helps seal the flange to the tank. So a bent cover might be a problem, but I don't think it's my problem.

I pulled the cover, and the tank seems pretty straight:



(The gooey stuff is petroleum jelly for the o-rings.) Because some of the cover bolts are longer than others, and the holes in the tank are blind, I put together some washers to simulate the depth of the cover. That way I could use attach all six bolts to the tank without the cover being in place. Here's how it looks installed:



The torque measurement for those bolts is only 5Nm. You can see from this photo that the flange doesn't appear flush with the bottom of the tank. I think the photo makes the gap look a little worse than it is, but still, it's not flush. There's also no gasket sealing the flange to the tank -- there's only an internal o-ring (which I replaced).

I reinstalled the pump assembly, started the bike and no leaks. 5-10 minutes later, it started leaking slowly. If you look at the bolt in the top of this picture, you can see that it's wet with gas:



You can't tell by the orientation of the photo, but that bolt is the near the lowest point in the tank, so it makes sense that that's where I'd see a leak.

I don't know how to progress from here. The bike only has 8,000 miles, give or take, and so I find it hard that the tank is warped or needs replacement. What do you guys think? Ducati have had a problem with plastic tanks warping and swelling, so this could be the same issue, but the bike is 10 years old and I don't expect any help from Ducati NA.

[Kurlon]

If it IS the plastic swelling, drain it, open it up as much as possible (no pump flange, no cap, etc) and setup something to blow air through it. Hopefully after a week or two it'll revert back to it's proper shape. If it does you can have it lined to prevent the swelling from recurring.

[myzx6]

Not sure if you mentioned if it was leaking before you took it apart, if it wasn’t before check the orings carefully to make sure you didn’t nick it anywhere but it is Most likely a swelling tank like has been said, wouldn’t hurt to check with Ducati because it is a very well known issue with there plastic tanks. Hopefully someday they finally get rid of the ethanol in our fuel because it really does more harm then good although they’ll prob just replace it with something worse.

[number9]

If it IS the plastic swelling, drain it, open it up as much as possible (no pump flange, no cap, etc) and setup something to blow air through it. Hopefully after a week or two it'll revert back to it's proper shape. If it does you can have it lined to prevent the swelling from recurring.

How can I tell it's swelling? I've posted on Ducati.ms but haven't had much luck there. I could put a straight edge on it, but I'm not sure if they are supposed to be flush from the factory. I'm sure it is supposed to be flush, though...

Not sure if you mentioned if it was leaking before you took it apart, if it wasn’t before check the orings carefully to make sure you didn’t nick it anywhere but it is Most likely a swelling tank like has been said, wouldn’t hurt to check with Ducati because it is a very well known issue with there plastic tanks. Hopefully someday they finally get rid of the ethanol in our fuel because it really does more harm then good although they’ll prob just replace it with something worse.

I can check the o-ring but I was very careful with it. The other thing I can try is using a fuel-safe sealant. But that seems like a bit of a hack job...

I called Cycles 128 today and they said they hadn't heard of Hyper tanks swelling. I guess I can call Riverside tomorrow and see what they say. But again, it's 10 years old, I can't imagine Ducati NA being helpful. There was a class action lawsuit in 2011 but that was good for bikes six years after manufacturer -- meaning I'm 4 years too late.

[whynot]

I bought my '12 Hyper 796 new in 2012, have never heard of Hyper tanks swelling. If I wanted to call a dealer, the only one I'd call is Seacoast. I'd try to reach Charles, but it's not like the old days, so you may not be able to get him on the phone. In that case. talk to Scott (Scott-in-Service, not Scott-in-Sales) or maybe better yet, Adam, he's been around these things long enough to know.

When I bought my Hyper I had Seacoast install the CA-Cycleworks 6.4 gal. tank. When they were removing the original tank, they told me that they found one of the fuel pump mount hole threads stripped. So they warrantied the original tank and gave me a new one, still in the box.

Here's another idea, maybe the fuel is leaking around or through the threads of the pump mount. Take a look at Loctite Thread Sealant (not thread locker).
Thread Sealant - Henkel

Not an answer to your question, just some ramblings ...

[number9]

I bought my '12 Hyper 796 new in 2012, have never heard of Hyper tanks swelling. If I wanted to call a dealer, the only one I'd call is Seacoast. I'd try to reach Charles, but it's not like the old days, so you may not be able to get him on the phone. In that case. talk to Scott (Scott-in-Service, not Scott-in-Sales) or maybe better yet, Adam, he's been around these things long enough to know.

When I bought my Hyper I had Seacoast install the CA-Cycleworks 6.4 gal. tank. When they were removing the original tank, they told me that they found one of the fuel pump mount hole threads stripped. So they warrantied the original tank and gave me a new one, still in the box.

Here's another idea, maybe the fuel is leaking around or through the threads of the pump mount. Take a look at Loctite Thread Sealant (not thread locker).
Thread Sealant - Henkel

Not an answer to your question, just some ramblings ...

I'll give Seacoast a call, I had totally forgotten about them - thanks. Looking at the parts diagram, the bolts do not use sealant from the factory.

A guy on another forum suggested checking out the breather valve. This is an interesting idea as the gas doesn't leak while the engine is running, but it leaks a few minutes after it stocks. His theory is that the vapor is expanding, can't get out of the breather valve, and so finds the next path of least resistance -- i.e., the flange itself.

[Tekime]

A guy on another forum suggested checking out the breather valve. This is an interesting idea as the gas doesn't leak while the engine is running, but it leaks a few minutes after it stocks. His theory is that the vapor is expanding, can't get out of the breather valve, and so finds the next path of least resistance -- i.e., the flange itself.

Not familiar with this tank, but also my first thought. Maybe just loosen the cap a bit after stopping?

[number9]

Not familiar with this tank, but also my first thought. Maybe just loosen the cap a bit after stopping?

Yeah, I'm going to give that a try in a few minutes.

[08zxcpb]

Razee's replaced the tank on my hyper so they should also be aware of it as well. Mine swelled and my plastics around the tank no longer fit right.

I need to look into this thermistor change as my bike's fuel light no longer works.

[whynot]

Razee's replaced the tank on my hyper so they should also be aware of it as well. Mine swelled and my plastics around the tank no longer fit right.

...

Good to know, I hadn't heard of problems with the Hyper tanks. What year is yours? Maybe by 2012 (last year of the air cooled) Ducati had it solved. [dunno]

[08zxcpb]

Good to know, I hadn't heard of problems with the Hyper tanks. What year is yours? Maybe by 2012 (last year of the air cooled) Ducati had it solved. [dunno]

Mine is a 2010. In the first 3 years of its life I had over 15,000 (now 23,000) on it so it got a lot of use quickly, not sure if that exacerbated it. Seems we have similar bikes both with Ninja 1000's. Any chance you have a zx6 as well?

[Kurlon]

AFAIK Ducati never changed the plastic they were using, so they're all going to soak up ethanol and swell. They did however get better at designing the tanks so that the swelling was accounted for and didn't cause issues, mostly?

[FriskyDingo]

I've got the same bike, 08, still on my original tank with zero swelling issues. I did have a very small leak issue at the fuel pump similar to your situation, however it was still under warranty & had it taken care of by the dealer(Razee). I can't recall what the exact issue was(it was not swelling), I'll see if I can dig up the receipt for the work done, if I can find it i'll post up what the fix was.

[whynot]

Mine is a 2010. In the first 3 years of its life I had over 15,000 (now 23,000) on it so it got a lot of use quickly, not sure if that exacerbated it. Seems we have similar bikes both with Ninja 1000's. Any chance you have a zx6 as well?

I've got 23K on the 2012 Hyper 796, fun bike. No ZX6 to go with my Ninja 1000. My other "modern" bike is a 2005 Multistrada 1000S that I bought used from Seacoast in November 2016, now has 15K miles, no tank swelling that I know of.

[number9]

I've got the same bike, 08, still on my original tank with zero swelling issues. I did have a very small leak issue at the fuel pump similar to your situation, however it was still under warranty & had it taken care of by the dealer(Razee). I can't recall what the exact issue was(it was not swelling), I'll see if I can dig up the receipt for the work done, if I can find it i'll post up what the fix was.

Would you mind posting what you found?

I actually broke the old breather valve while trying to remove it. I got a new one from Ducati Omaha (part no. 59340351A, $52.27) and it seems to have fixed the problem. I'll go for an extended ride on Friday to see what happens...

[scottieducati]

If it hasn't fixed it... or if you just want stoooopid fuel capacity (6.4 gallons!), I can help you with one of these.

[loudbeard]

If it hasn't fixed it... or if you just want stoooopid fuel capacity (6.4 gallons!), I can help you with one of these.

I like how there's a choice of ECU.

Would you like the Siemens or this Italian piece of crap?

[number9]

If it hasn't fixed it... or if you just want stoooopid fuel capacity (6.4 gallons!), I can help you with one of these.

I'll let you know! The current tank is (supposedly) good for 100mi or so.. which is probably good for me.

I like how there's a choice of ECU.

Would you like the Siemens or this Italian piece of crap?

Italians, fucking.

[number9]

Is anyone familiar with breather valves -- did I assemble this thing correctly? It came disassembled, with no instructions.



I double-checked the hose and it is not clogged. When I put the breather together, I have to blow hard to get any air through it. Does that sound correct?

Jokes from loudbeard should go below.