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2008 HyperMotard 1100S
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Discussion Starter · #1 ·
After replacing the fuel filter and the thermistor for the low-fuel light, and installing a new o-ring for the flange, I've got a new problem. Specifically, a fuel leak.

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. With the flange cover on, you can't really tell where the leak is coming from. So I took the cover off. 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:



I pulled the cover, and the tank looks 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. Here's how it looks installed:



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:



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?

:frown2:
 

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I'd think about the fuel flange gasket as an obvious suspect first. You mentioned vaseline for the fuel line O-rings but did you put some on the flange gasket? A bit of lube could help it find a better seal.

Could be that the gasket was damaged in transit or in installation. As a bodge, you could try an instant-gasket type product that's safe for fuel (eg Permatex No 2). If that works, then you know where the problem is and deal with it accordingly.

If not, then you might have to start thinking about the tank ...
 

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Discussion Starter · #3 ·
I'd think about the fuel flange gasket as an obvious suspect first. You mentioned vaseline for the fuel line O-rings but did you put some on the flange gasket? A bit of lube could help it find a better seal.

Could be that the gasket was damaged in transit or in installation. As a bodge, you could try an instant-gasket type product that's safe for fuel (eg Permatex No 2). If that works, then you know where the problem is and deal with it accordingly.

If not, then you might have to start thinking about the tank ...
There's no gasket on there. When I took the pump & flange assembly out, there was no gasket. I looked in the Spare Parts Cattledog and there's no gasket shown -- just the o-ring for the flange itself. Screenshot is attached.
 

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There's no gasket on there. When I took the pump & flange assembly out, there was no gasket. I looked in the Spare Parts Cattledog and there's no gasket shown -- just the o-ring for the flange itself. Screenshot is attached.
Yes sorry I use the terms gasket and o-ring more or less interchangeably. I meant the o-ring - could've been damaged at some point in transit or installation. To me that makes more immediate sense than the fuel tank warping in the time it took for you to replace the thermistor and fuel filter (since you didn't mention it leaking before you did those fixes).
 

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Mine leaked after I fixed my thermistor as well. I backed off the screws and re-torqued to spec (don't recall but very light) and the problem went away. FYI Better O-Rings are available from Ducati and California Cycleworks.

t_bare
 

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Discussion Starter · #6 ·
Yes sorry I use the terms gasket and o-ring more or less interchangeably. I meant the o-ring - could've been damaged at some point in transit or installation. To me that makes more immediate sense than the fuel tank warping in the time it took for you to replace the thermistor and fuel filter (since you didn't mention it leaking before you did those fixes).
No worries. I just got a bit worried in case there was supposed to be both an o-ring and a filter! I'll double check the o-ring but I was very careful with it. It took a bit of sourcing to find one...

A guy on another forum suggested I check out the breather valve. He's wondering if the breather valve is stopping the vapors from escaping once the tank warms up, and as such the pressure can't go out the valve and instead finds the next path of least resistance, which in this case is the flange.

Mine leaked after I fixed my thermistor as well. I backed off the screws and re-torqued to spec (don't recall but very light) and the problem went away. FYI Better O-Rings are available from Ducati and California Cycleworks.

t_bare
It's 5 Nm I think, which is about 44 inch-pounds. I have a 1/4" torque wrench, but I almost don't trust it at such low values, so I'm literally tightening them by hand.

Today I'll put more gas in the tank, run the engine again, switch it off, and open the gas cap. If it doesn't leak, then that should mean the problem is the breather.
 

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Discussion Starter · #7 ·
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...
 
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Mine started leaking again. Just a few drops when I'm not looking, I find gas on my hugger and swing arm

t_bare
 

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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...
Was it a breather issue?

t_bare
 

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Discussion Starter · #10 ·
Was it a breather issue?

t_bare
I think so. I broke the old breather when trying to remove it, so I never had a chance to test it. But, with a new breather valve installed, the problem has gone away.
 
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I suspect mine is slowly oozing when I don't ride the bike for awhile then when I run it first time it pushes bunch of old nasty gas out.

It will not leak when I am looking. I've picked up a couple of size 341 Viton O-rings from Amazon for under $5. I have also put a little silicon in the breather valve. Hopefully I've stumble into the fix.

t_bare
 

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Discussion Starter · #12 ·
I suspect mine is slowly oozing when I don't ride the bike for awhile then when I run it first time it pushes bunch of old nasty gas out.

It will not leak when I am looking. I've picked up a couple of size 341 Viton O-rings from Amazon for under $5. I have also put a little silicon in the breather valve. Hopefully I've stumble into the fix.

t_bare
I got an o-ring from eBay for about $10. It came from these guys: Plebeo. The website is a bit simple but the service & support was first-rate. The first o-ring they sent didn't fit, but they shipped another one free of charge and I had it in a few days. Apparently there are two different sizes for flanges..! I'd gladly use them again.
 

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Discussion Starter · #13 ·
The problem has returned. :(

Everything was going fine, until I came home one day and there was gas all over the garage floor. Opened the fuel cap and heard a very distinct "woosh" noise.

Either the new vent isn't working, or the vent hose is blocked somewhere..?
 
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Discussion Starter · #14 ·
Anyone? :(
 

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sounds like a vent issue as you say.tried using compressed air to see if the lines are clear? is the vent valve installed correct way? tank vent hoses installed correctly?
 

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Discussion Starter · #16 ·
This ended up being a combination of issues: the breather was not venting properly, and the bottom of my tank was slightly warped. 😖 I got a replacement tank from a friend for $150 (with breather!) and my problems have so far gone away.
 
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This ended up being a combination of issues: the breather was not venting properly, and the bottom of my tank was slightly warped. 😖 I got a replacement tank from a friend for $150 (with breather!) and my problems have so far gone away.
My problem turned out to be a nicked wire and the fuel was running through it. I little epoxy and it has been good ever since.

t_bare
 

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Discussion Starter · #18 ·
My problem turned out to be a nicked wire and the fuel was running through it. I little epoxy and it has been good ever since.

t_bare
I guess sometimes it's the simple things :(
 
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