Tank leaking from plate

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Jul 25, 2022 | 02:53 PM

House O' Payne

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From: Santa Barbara, CA

Tank leaking from plate

My 2011 Crossbones tank required me to open it and clean it out (I'll spare the reader the long story of why). When shopped for the replacement parts (10 screws and new rubber gasket) I was surprised to learn the parts had been revised from what I had. Just to be sure I had the right parts, I ordered a set of the old and the new. Since the newest revision of the parts appeared to be made to better seal the tank (e.g. rubber gaskets for each screw verses plastic) I sealed the tank with the new version parts, making sure I followed the 'Fix My Harley' tightening sequence. The tank seal was fine for the first tank fill, but as soon as I needed to refill the tank, it started leaking again. I ordered more screws (since they are single use) and this time I covered the tank plate seams (where the plate contacts the tank) with a non-permanent gasket sealer 'goop' that claims to be resistant to gas.

Two more tank fills with no leaks and then last weekend after a tank fill the tank began leaking AGAIN.

Upon examining the plate, it appears some of the tank screws had worked themselves loose, even though they were tightened to the point where I could see the rubber gasket under each bulging. These are supposed to be 'self-tapping' so no loctite was recommended, and I'm not sure it holds up to gas anyway. I retightened the screws and reapplied more sealant 'goop' but honestly I have no faith this will hold and fully expect more gas leaks.

PLEASE ADVISE, especially anyone who's found a solution to this f-ing frustrating

problem.

Thanks!

Jul 26, 2022 | 09:49 AM

hattitude

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From: San Diego, CA

Revised parts numbers happen all the time. It could be just a change in vendor, or an improvement to the part. The parts shouldn't be the problem....

Did you follow the procedure in the Service Manual...?

Did you torque the sealing screws or just tighten them until the gasket "bulged"....?

FWIW.... per my 2003 Softail Service manual, after saying to loosely install all top plate screws, it says:

"Tighten sealing screws using cross pattern to 18-24 in-lbs (2.0- 2.7 Nm)"

Over tightening can cause as many issues and under tightening.... Using the cross pattern allows the gasket to sit and seal properly...

I wouldn't use any sealant if not called for by the service manual... unless I determined my tank mounting surface for the gasket is somehow compromised..

Last edited by hattitude; Jul 26, 2022 at 09:58 AM.

Jul 26, 2022 | 12:19 PM

House O' Payne

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From: Santa Barbara, CA

Quote:

Originally Posted by hattitude

I followed the tightening sequence exactly, after I wrote the sequence numbers in permanent marker below each mounting hole on the mounting plate. I finger tightened first, in the specified mounting order being careful not to cross thread, but since I don't own a torque wrench that goes down to 20 -ish in-lbs. I guessed that a slight bulge in the washer would be normal, so I stopped tightening when it felt snug and there was a bulge. My guess is that I didn't tighten enough, since most of the screws loosened. As for using the sealant, I had already determined the seal was compromised when my bike began gushing fuel so badly I had to have the bike towed home. If making the plate a little messy to take off next time will save me a gas leak, it's well worth it to me.

I'm planning on ordering another set of plate screws, new gasket, and a new torque wrench that goes down to 20 in-lbs. If the screws are truly self-tapping (as I read they are) it makes no sense to me that they would easily back out.

The liquid gasket seal I'm using dries tacky, and removable, so I'll probable use it again just for 'insurance'.

The first time my tank leaked fuel, I was so new to the bike I didn't even know there was a plate under the speedo, and I wasn't carrying any tools. I had to call a tow truck to get the bike home. Now, I'm carrying tools so hopefully if the bike starts gushing gas again I can just tighten the mounting screws enough to get me home without a tow. I'm actually a little PTSD now about filling my tank!

I'm seriously thinking about sealing the heads of the screws after they are tightened down with something I can break them free of later when I need to.

Jul 26, 2022 | 12:50 PM

hattitude

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From: San Diego, CA

Quote:

Originally Posted by House O' Payne

I'm planning on ordering another set of plate screws, new gasket, and a new torque wrench that goes down to 20 in-lbs. If the screws are truly self-tapping (as I read they are) it makes no sense to me that they would easily back out.

To be fair.... they are only self-tapping the first time they are screwed into the metal of the tank.....

You can reuse self tapping screws as long as the threads in the metal that were formed during the initial "tapping" are not damaged...

I'm not a mechanical engineer or a machinist, but I would suspect after the initial tapping... it's the torque that holds them in place like any other screw/bolt...

Just thinking out loud.... but did the screws work loose.... or is it possible the threads got somehow damaged....??

Jul 26, 2022 | 07:21 PM

House O' Payne

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From: Santa Barbara, CA

Quote:

Originally Posted by hattitude

Just to be clear, the screws I used the first time the plate leaked were brand new, and were the latest revision (have rubber washers affixed) installed with the latest version gasket. These somehow backed out to leak again, and so far I just re-tighted them, not replaced them. There is no reason so far for me to suspect the threads in the plate are damaged, since the plate/tank wasn't leaking when I first bought the bike, and I pulled off the plate originally not because it was leaking, but to clean out the tank, replacing the screws with new ones, as described. All told only new (not reused), 'self-tapping screws were installed and I'm pretty sure the metal of the screws is too soft to strip out the plate threads. I've read of the plate threads being stripped, but not by the screws meant to hold it on.

Anyway, I'm pretty confident the plate threads aren't stripped....

Jul 27, 2022 | 11:15 PM

Clammy

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From: Ottawa, CANADA

I can tell you from experience that proper torque, and sequence, are critical for that top plate. It's not one of those components you can "wing it" on. Even a little too tight on those screws will cause a leak. One thing I can recommend is a non-hardening sealer such as hylomar if your tank's mating surface isn't perfect.

Cheers!

Jul 28, 2022 | 03:37 PM

ThePaintPirate

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Joined: Dec 2013

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From: SE Iowa

Quote:

Originally Posted by Clammy

I concur. When I replaced the tank on my Train, I over tightened the bolts ever so slightly and it caused a leak that ruined a small section of my paint. Follow the proper sequence and torque to spec.