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Discussion Starter · #1 ·
Just swapped out all my internal hoses inside my tank for new ones on my 916 and replaced the quick connects, when I reconnected everything and went to go put gas in it I noticed gas was leaking out at the connection from the sending unit to the tank. It seems that the tank is slightly dented where the sending unit connects to which is causing the leak I can try to bend it a little bit to try to get it level but I'm kind of against forcing it too much is there a gasket or gas proof caulking of some kind that can be used when I reattach it to seal it?
 

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Is the plastic nut cracked???? Mine was slightly cracked and wouldn't tighten things properly. Had to switch to an aluminium one which works great. Think I got it from Motowheels.
 
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Discussion Starter · #3 ·
Is the plastic nut cracked???? Mine was slightly cracked and wouldn't tighten things properly. Had to switch to an aluminium one which works great. Think I got it from Motowheels.
Its not the nuts (plastic quick releases) i replaced those with the metal ones, and I also got mine from motowheels. They are such a good upgrade! But... thats not the current issue...The issue is the sending unit, the whole round disk that mounts to the tank, the 4" or so wide hole in the bottom of the tank is not perfectly level, so when I attach the sending unit there is a slight gap even when tightened down. There was some residue not sure what it was, but it was definitely there where the sending unit was originally attached to the tank. I'm not sure what the original owner used but it looks like some type of either caulking epoxy or liquid gasket filler was applied between the sending unit and the tank itself.

Im also assuming the issue preexisted prior to my upgrades and thats why that stuff was there.

I have a 2nd track tank and was just going to swap it out, but the seat at the bottom does not look like its in any better condition then whats on my bike... clearly this previous owner used something I'm just trying to figure out what it was so I can use it too...or if there's another option for me....
 

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Is the plastic nut cracked???? Mine was slightly cracked and wouldn't tighten things properly. Had to switch to an aluminium one which works great. Think I got it from Motowheels.
Its not the nuts (plastic quick releases) i replaced those with the metal ones, and I also got mine from motowheels. They are such a good upgrade! But... thats not the current issue...The issue is the sending unit, the whole round disk that mounts to the tank, the 4" or so wide hole in the bottom of the tank is not perfectly level, so when I attach the sending unit there is a slight gap even when tightened down. There was some residue not sure what it was, but it was definitely there where the sending unit was originally attached to the tank. I'm not sure what the original owner used but it looks like some type of either caulking epoxy or liquid gasket filler was applied between the sending unit and the tank itself.

Im also assuming the issue preexisted prior to my upgrades and thats why that stuff was there.

I have a 2nd track tank and was just going to swap it out, but the seat at the bottom does not look like its in any better condition then whats on my bike... clearly this previous owner used something I'm just trying to figure out what it was so I can use it too...or if there's another option for me....
Just my $0.02, but I would imagine thef tank would have to be pretty distorted for the seal to breech. A slight gap shouldn't cause a leak, and is likely normal on these tanks. If it is like the 748 (should be), then the rubber seal does not seat against the bottom of the tank, but the inside of the tank flange. Did you use a new gasket? Did you scrape off the old sealant that the previous owner had on it? Did you clean the mating surface, inside the lip of the tank where the sending unit goes in? When you look at the gap, can you see the o-ring seal?

I always recommend a new o-ring whenever you have to pull the sending unit. I just bout a Vitron from Ebay for under $9.00, shipped. The old seal may not look damaged, but can become distorted upon removal of the sending unit. One last thing to check. If you look at your sending unit, you will see that there is a shelf for the O-ring to rest. Some people think that it rests all the way on the mounting flange... It does not. To make matters worse, the OEM seal fits loose, and often slips down to the flange. This will definitely cause a leak. In order for the seal to function properly, it has to seal between the sending unit and the lip of the tank, not the bottom of the tank. I actually have mine off, and can show you, if that will help. Just let me know. I'm betting that your seal slipped off the shelf, and down against the mounting flange. That will definitely cause a leak.
 

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By the way, I am upgrading to the metal fuel line quick disconnects, myself. If you have not done so, I highly recommend putting a wrap of Teflon tape on the threads. This will help seal them to the pump assembly, better, as you are now going metal to metal.
 

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Here ya go. This is where the seal SHOULD be. Note that it does not go up against the flange, where the bolt holes are. This allows it to seal up against the inner lip of the fuel tank. Also, if you reuse your old seal, it is likely stretched and will fit loose. This greatly increases the likelihood that the seal will slip off this shelf, and fall up against the flange, causing a leak. This is why I recommend a good pair of scissors, when it comes to changing the fuel pump or filter. The scissors are to cut the old seal in half, that way you won't be tempted to reuse it. ?
Clean both the inner lip of the fuel tank, as well as the sending unit. Apply a liberal amount of Vasoline to both the seal as well as the tank lip, and apply even pressure when reinstalling the sending unit into the tank.
 

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The part of the tank you describe as dented is not really an issue as mentioned above. I think mine looks like that as well. The three bolts that mount the fuel pump assembly have zero effect on the actual sealing of the tank and only hold it from dropping out really. The sealing happens between that o ring and the surfaces it fits against. Nicking it is a pretty common thing to have happen, especially if you're new at messing with it. There are a few things to do that can prevent it from leaking. Loads of calking or other sealants is not one of them...

The trick is to not nick it when installing! You need to remove any burs in the tank flange for one. I have used wet/dry sandpaper and pretty much polished the tank side flange to a smooth and shiny surface. Then use lots of lube. I have a tube of Sil-Glyde rubber grease (NAPA) that I use on this, as well as the quick disconnect o rings. Just a very thin coat between the pump assemble flange and o ring, and then a little heavier on the tank flange and the o ring. Get 3 longer bolts to temporarily replace the special bolts that hold the flange in place. Not too long so they bottom out in the tank, but long enough to get a bite with the pump assemble just resting there. Tighten to walk the assembly in to the tank evenly and not pinching the o ring. Once the o ring is in, remove the longer bolts and push it in the reset of the way with your hand. Bottoming the bolts in those crimped in threads would be unfortunate...

Last, it's better to not reuse that o ring. They are stupidly expensive from Ducati. You can find them on your own for a dollar or two.

The size you need is 4-5/8 ID X 4-7/8 OD X 1/8 W made of Viton rubber with a durameter of 75A. It has a Mil-spec number, M83248 that makes it pretty easy t find. If you get one on your own, it will not be green. That's OK. The green is just the color used to indicate fuel system use. Viton rubber o rings can be black.

Edit:

The other place you can have a leak is at one the three crimped in thread inserts on the tank. One of mine has a hairline crack. If left alone, it will drip fuel. As a "temporary" fix (that I did 3 fuel filter changes ago) I use a dab of Seal-all 380112 on the threads. It is a oil and fuel resistant adhesive. My plan was to Caswell coat the tank, but sealing the threads did the trick, three times now, so I still haven't sealed the tank.
 
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Discussion Starter · #8 ·
Thanks everyone, the rubber seal is definitely distorted, it seems like its stretched out and needs to be replaced. It does not sit on that lip any more as its now slightly bigger.

I am going to get a new seal and start there as well as clean up the whole seat.

Thanks again guys.
 

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Thanks everyone, the rubber seal is definitely distorted, it seems like its stretched out and needs to be replaced. It does not sit on that lip any more as its now slightly bigger.

I am going to get a new seal and start there as well as clean up the whole seat.

Thanks again guys.
Yeah, I thought that was going to be the case. This is the one I purchased.
https://m.ebay.com/itm/DUCATI-Tank-...t-88650011A-/163058797981?txnId=1721743051006

I went with it, because it was just easier for me to get it off of Ebay, than to try to hunt down the correct size, and I didn't really feel like getting a second mortgage on my home to get a stupid little seal directly from Ducati. SS904 has some great tips, definitely follow them, and you should be fine. I would add that if you are going to polish the flange, make sure that no sanding grit falls into the tank. Just a heads up.
Good luck, and keep us posted how it all went.
???
 

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Discussion Starter · #10 ·
Yeah, I thought that was going to be the case. This is the one I purchased.
https://m.ebay.com/itm/DUCATI-Tank-...t-88650011A-/163058797981?txnId=1721743051006

I went with it, because it was just easier for me to get it off of Ebay, than to try to hunt down the correct size, and I didn't really feel like getting a second mortgage on my home to get a stupid little seal directly from Ducati. SS904 has some great tips, definitely follow them, and you should be fine. I would add that if you are going to polish the flange, make sure that no sanding grit falls into the tank. Just a heads up.
Good luck, and keep us posted how it all went.
???
Thanks! I also went with ebay, I saw that one but ordered this one as it had next day shipping available

https://www.ebay.com/itm/Fuel-Petro...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
 
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