Pressure in fuel tank

[motorplex88]

Acquired an 80 model wide glide late last summer and finally got around to taking it out on a shake down run. Riding with some buddies for about 70 miles and decided to stop in a place for a beer and a burger. Parked out in the direct sun and was in the joint for about an hour. Came out to find fuel all around the bike. I knew I shut the fuel off, so upon inspection found the left tank rear mounting tab with a hairline crack where it joins the tank. Was going to drain the left tank and just run off the right. Went to take the left fuel tank cap off and the thing had so much pressure in the tank it blew the cap out of my hand. Checked the vent it the right tank and seems fine. After the pressure was off,  the leak pretty much stop ed so I went ahead and rode it home with no issue I still have to fix my tab but I can't ever remember by gas tank building pressure. Any thoughts.

[JW113]

Mine gets pressurized as well, never to the point of blowing the cap off though. I think by design they're supposed to be that way. The valve in the right side tank lets air in, but does not let it out.

-JW

[motorplex88]

I suppose just sitting out in the hot sun on an 80 degree day made for excess pressure. I will pull the tank and repair. Hopefully I won't have to re-paint. I just thought it was unusual to have THAT MUCH pressure. The bike ran flawless otherwise. Makes my other shovel seem like a sissy !

[JW113]

I have found the pressure goes up as the fuel level goes down. How much gas was in the tank?

If you don't want to repaint the tank (rhetorical), then clean the paint from the cracked area and JB Weld it. And have the tank cleaned out and coated with Red Kote at a radiator shop.

-JW

[xlfan]

The  vent/equalizer tube under instrument panel is open in both ends?

[motorplex88]

The tank was about 1/2 full . To be truthfull I never thought about the top crossover vent tube. I will have to check that out. I think I can get away with just tig welding the small crack at the tab without a re-paint. When I got the bike, all of the existing tank liner had deteriorated badly and had to be cleaned out. Probably was leaking in the first place and previous owner did a poor job of lining the tank. Don't know for sure as the bike was in storeage for a long time.

[david lee]

make sure theres no petrol fumes in tank before welding.you dont want a big kaboom

[JW113]

If the crossover vent tube is not connected, there will be no pressure as that line is to allow air from the right tank into the left tank. No line, it all vents to the air. Not good in a closed garage with water heater or gas dryer.

If you can weld it, even better. I think when they weld gas tanks, they keep a purge line of nitrogen or helium flowing into the tank.

-JW

[Coff 06]

Dry ice also works great to neutralize the tank for welding.Usually easy to find.        Coff 06

[Hossamania]

If the crossover vent tube is not connected, there will be no pressure as that line is to allow air from the right tank into the left tank. No line, it all vents to the air. Not good in a closed garage with water heater or gas dryer.

-JW

Not good in any garage.

[motorplex88]

Welding gas tanks is a everyday occurrence to me.  Drain, steam clean, and purge with inert gas while welding.  I'll pull it apart, give it a fix and ride her some more. I'll report the results. Oh, I also need to true the front spoke wheel.

[Racepres]

Welding Fuel tanks is Not something I undertake... leave that to Professionals...
the Product Known as Seal All


works miracles, and lasted about 5 years on the Side mount of a Shovelhead here..

[a_disalvo]

Permatex makes an epoxy just for fuel tanks, I have used it with excellent results. Frank

[PoorUB]

One more vote for Seal All. I have used it many times to seal leaking fuel tanks.
I worked at a real service station in high school.  That is where I first used it. I would have someone bring in a car with a tiny pin hole in the tank. I would tank emery cloth and clean the area of the hole down to clean metal. They usually dripped fasted then. I would put a glob of Seal All on one finger and the air hose in the other hand. Blow the hole off to dry it off and jam the finger of goo over the hole. It might have taken 2-3 tries but I could get it to stop. Then 2-3 more coats of Seal All and no more leaks.

[motorplex88]

After I get the tank off and onto the bench I'll see how bad it is. I might try the sealant route but I've been welding professionally for 40 years so that's just the way I normally go.....but I'm always willing to try a product that I have never used before especially if others have had good luck with it. I probably won't get to it till the end of the week because any more by the time I get off work, all I want is my recliner.

[david lee]

cant see that stuff working on a mounting point.but worth a try i spose

[Hossamania]

If I were able to safely and competently weld it, that would be my first choice.

[PoorUB]

Yes, if it is cracked at a mount, I would weld it.

[motorplex88]

 I'm not the first guy to be working on this.

[motorplex88]

Out of the blaster and on to steam. I should have taken a picture of the wad of epoxy that was there.

[JW113]

Hey I'm always up for information exchange. So what is your method?

-JW

[david lee]

definitley a weld job from memory that mounting point has a spacer and if not installed theres to much pressure when the bolt is tightened

[motorplex88]

Don't laugh 😂. Man this thing is turning out to be a bitch. I'm guessing the tank liner is messing with me cause crap keeps blowing out of the weld. I was surprised that the steam clean didn't take  all of the liner out but some remained. It's holding pressure finally. To be honest I would not know if this is a knockoff tank or not. I know it's damned thin. The spacer was present upon disassembly and nothing seems in a bind.. obviously someone has been working on it before so who knows what really happened before hand.  JW. On this particular one , I dug all the epoxy off, sandblasted, ground all the previous welds off and steam cleaned the inside. There was not even a whiff of gas fumes left so I went to welding. If I detect any fumes at all I will purge the tank with whatever inert gas I have available (argon, nitrogen, helium ect.). I now no why the previous repair was finished with epoxy. They got tired of pin holes blowing out 

[david lee]

it might need reinforcing around the mounting point. if the metal is thin it will more than likely keep cracking

[JW113]

If it didn't go Ka-BANG at the first application of the heat, I think you're probably OK. If it were mine, I would still have it lined with Red Kote and not worry thereafter. Who knows how many more rusty thin spots are lurking inside.

Good luck with it,
-JW

[motorplex88]

I'll thread a long bolt in it tomorrow and see if there is any flex and then re-check for leaks. If all seems good I might put some off that seal all on it, prime and paint the repaired area. Rattle can will be fine as it's not seen. Anything more and it's new tank time
They just ain't worth it.

[kd]

A fine fluxed bronze rod then silver solder over all of the welds and leaks. It's tougher than regular solder yet still flexible.  Then clean an buff the surface with fine grit to bring up fresh metal. Hot iron a layer of lead solder over the complete work area. You'll have steel welds sealed with silver solder and backed up with lead.   This has worked well for me on unbelievably bad tank holes. The lower heat used in the silver and lead solder doesn't pull contaminants into the puddle.

[Racepres]

Hey I'm always up for information exchange. So what is your method?

-JW

Utilizing Stock, The rule is; do Not put anything in any kind of Bind.. bend tabs, add spacers... whatever it takes to Not push, pull, twist..  Never failed me yet...
Aftermarket crap.... Good luck!  best advice? Use O.E.

[JW113]

Yeah, that's essentially what I do as well. Shim the tanks to the frame mount points. Luckily I have stock tanks, but finding OE is getting harder and harder. No doubt certain aftermarket brands are garbage, but are there no quality tanks being offered by anyone? I haven't really looked. The tanks on my Indian are not stock, but in fact far superior to the stock thin steel soldered OE tanks. They are heavy gauge water formed steel, and TIG welded. There is a far bigger market for HD parts than old Indians, so why no similar made tanks available?

-JW

[motorplex88]

Well here is the ugly. Impurities abound but holds about 10 psi. I'm tired of phuckin with it and will put it back together. As KD mentioned I thought it would be a good idea to put some bronze rod on it but crap just keeps sifting through.  I've been here before. Know when to say when. I'll put on some self etching primer and and a little black and see how long it lasts. It does seem strong at least. I see new tanks in my future. Hope I can find something decent. Thanks for all the thoughts and comments. I'll post the finished product when it's all back together.

[motorplex88]

This should have been with last post

[76shuvlinoff]

Had a leaking crack on an aftermarket FLH tank at the upper rear mount. Cleaned it up the best I could, put a Napa gas tank patch over it then JB weld over that.  It had fresh paint and I wanted to ride. I had pressure tested before the paint job for 7 psi, figured I was good. I planned on fixing it right the next winter. That was 13 years ago.

[crock]

It may be blasphemous, but I converted my 73 flh to flat side tanks about 10 years ago. https://www.jpcycles.com/product/7200055/biker-s-choice-flatside-tank-economy-mounting-kit?redirectedKeyword=7200055&totalResult=1
bought a set of oe tanks from a wreck (actually 2 different wrecks one from each side) and never looked back

[Racepres]

It may be blasphemous, but I converted my 73 flh to flat side tanks about 10 years ago. https://www.jpcycles.com/product/7200055/biker-s-choice-flatside-tank-economy-mounting-kit?redirectedKeyword=7200055&totalResult=1
bought a set of oe tanks from a wreck (actually 2 different wrecks one from each side) and never looked back

But... They Never look quite Right...IMO
Learn to Mount the O.E. and Carry on..
Oh... I like the Flatsides on the 1985 1986 Models!!! But the Frame is a bit Different.. [LOL, Understatement]

[crock]

It may be blasphemous, but I converted my 73 flh to flat side tanks about 10 years ago. https://www.jpcycles.com/product/7200055/biker-s-choice-flatside-tank-economy-mounting-kit?redirectedKeyword=7200055&totalResult=1
bought a set of oe tanks from a wreck (actually 2 different wrecks one from each side) and never looked back

But... They Never look quite Right...IMO
Learn to Mount the O.E. and Carry on..
Oh... I like the Flatsides on the 1985 1986 Models!!! But the Frame is a bit Different.. [LOL, Understatement]

hey are a little different. Had to modify the dash a little as I recall but no one has noticed it but me

[Hossamania]

Oh they notice, they are just polite enough not to say anything...     

[hbkeith]

Permatex makes an epoxy just for fuel tanks, I have used it with excellent results. Frank

I used this on a old truck with damn near a stream of gas coming out , lasted the year I had the truck

[kd]

Well here is the ugly. Impurities abound but holds about 10 psi. I'm tired of phuckin with it and will put it back together. As KD mentioned I thought it would be a good idea to put some bronze rod on it but crap just keeps sifting through.  I've been here before. Know when to say when. I'll put on some self etching primer and and a little black and see how long it lasts. It does seem strong at least. I see new tanks in my future. Hope I can find something decent. Thanks for all the thoughts and comments. I'll post the finished product when it's all back together.

If it's not too late, consider cleaning that surface up and using a hot iron to sweat a solder cove on that.  The hot iron won't pull anything into the puddle and it will bridge the small spots to guarantee a no leak seal.

[motorplex88]

In the words of Buck Owens, "Together Again". I deferred from the solder and sealant and will see what happens. With a little shimming here and there, things mounted with no stress or pulling of the mounting points. I should have showed  the other horrible repair work on the other tabs and you would know why I'm not spending any more time on these cockroaches.

[JW113]

Looking good! Nice truck too. '62?

-JW

[motorplex88]

Yup, my daily work truck

[Hossamania]

Motorplex, I sent a pm.

[david lee]

Yup, my daily work truck

which one drips the oil ?

[crock]

Oh they notice, they are just polite enough not to say anything...     

[motorplex88]

DL, I'm sure you know the answer to that question. 

[david lee]

DL, I'm sure you know the answer to that question. 

got a rough idea