I have a 2008 HM1100S. A couple of years ago I pulled the fuel pump assembly out to replace the fuel filter and replace the thermistor, because my low fuel light never worked. But re-installing everything and installing a new o-ring for the flange, I've got a new problem: specifically, a fuel leak. It's appears to be coming from the bottom of the tank, where the fuel pump mounts to a flange on the tank itself. 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. Apart from a bad thermistor, this tank has never given me any issues: (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 carefully at the bolt in the top of this picture, you can see that it's wet with fuel: At the same time as the gas tank started leaking, I started noticing a distinct whoosh sound whenever I opened the gas cap. I can't tell if it's positive pressure or a vacuum, but I tried checking the breather valve that sits on top of the tank. I, um, broke it while checking it, so I installed a new one. It didn't come with instructions, so this is how I installed it: Did I assemble it correctly? I have to blow very hard to get any air into the tank. I also checked the rubber hose for blockages, and it flows freely. What am I missing here? The fuel pump is severe enough that I can't chance riding the bike. Up until a month ago I've been 2 hours from the nearest garage, but I guess I could find someone to take it to now...
I can’t really help with the breather question as I’ve not had mine apart ( yet) But surely the leak has got to be the big o ring. The offending bolt is outside of where the o ring is so surly it must be letting by for fuel to be leaking around that bolt. Saying that. Is there anyway of that bolt/threaded insert from penetrating through the bottom of the tank or something?
I'll check this weekend. The reason that I suspected the breather is that the tank really makes a loud WOOSH when you open it, and that is something that did not happen before I changed the thermistor (and o-ring). So I started to think maybe the tank isn't venting properly..? If the problem was the o-ring, I would expect the tank would leak whenever it has gas in it -- but it doesn't. It only leaks after a while, and it absolutely pisses out if you've been riding the bike.
Right I get what your saying. Can you not somehow leave the cap loose and go for a steady ride on a strait road lol. At least that would rule the breather out
Are you sure the o-ring is seated correctly and doesn’t have any nicks in it? I assume it is the correct petrol resistant viton o- ring? The swollen rubber bush on the flange is most likely due to petrol leaking into it and it not being petrol resistant. I can’t help with whether the breather valve is installed correctly as it’s different to the ones on my bikes. However, it occurs to me the breather valve is not working as it should, the bike runs, a vacuum builds in the tank which is causing the o-ring to be pushed into the tank due to the pressure differential which opens the seal allowing fuel to drop out under gravity. I would double check the o- ring & fix the breather valve. All an hypothesis.
That's a good idea, I'll try and do that before it gets too cold. Gives me an excuse to bolt her back together, at least... I installed it about 2.5 years ago; I went away to graduate school soon after so the bike didn't get much use. I used this Viton o-ring; the first one they sent me was way too big so they sent a replacement. I was careful installing it, but there's still a chance I nicked it or did it wrong. Aside from riding the bike with the cap off, can you think of how I could test this? I guess I could try and temporarily gut the innards of the breather: that way there's no valve in it, just free movement of air through the hose (and I can keep the gas cap on!)
Just have a few litres (1 gallon) in the tank and ride with the cap open but over the filler, then refill and do the same with the cap sealed closed. See what the difference is. With only 1 gallon in there it will slosh around but won’t slosh out.
I just reassembled the breather; I can breathe into the open end of the hose and into the tank fairly easily. I can also suck air out of the tank as well I think. I'll put it back together and go for a ride with a gallon in there and see what happens. I'll make sure to park it at in my neighbor's spot when I do the other thing I was thinking of was filling the tank to the brim with water and see if any leaks over a week or so.
I wouldn’t do the water one, you’ll never get it fully dry, it could lead to rust and at the very least you run the risk of getting a gooey emulsion block up your injectors.
You had this problem in June 2018. Same problem and images. http://www.nestreetriders.com/forum/f7/hypermotard-gas-tank-leaking-91317.html
Correct, but I never got it fixed. I left to go to graduate school in New Hampshire in July of that year, and graduated earlier this year. I used the Viton o-ring I posted above; I think it was this one based on my old emails. That recall notice is for Multistradas, but are you saying there's a Hypermotard recall as well? I'll pick one of those up if problems persist, thanks.
The Hyper is the same sender unit fitment so yes - the part numbers were upgraded on the Hyper parts lists too.
Any reason to go with the new Ducati part number instead of CA Cycleworks' version? I checked my VIN against the NHTSA for good measure, and no open recalls for anything.
Bringing this back up, as springtime is coming eventually: I thought I'd read that there are actually two sizes of the o-ring, and they are significantly different in size. Does this jog anyone's memory? I think the next thing I should do is order 886.4.188.1A to replace the existing o-ring that's on there now. Thanks to Exige for pointing me in the direction of the recall! It looks like they're $31 new from the dealer.
