Blew up my gas tank last night

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BillT

BillT

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Tried to fix my leaking/weeping filler neck on the Pakistani tank on my Roadster. Soldered it with silver solder, and thought I did a pretty good job, without messing up the paint too bad. I wanted to test the seal, and decided to cork the filler neck with a plumbers test plug (inflatable rubber thing that slips into a pipe for pressure testing) install the taps, and put some air into the tank.

Worked like a champ, except while spraying soap around the neck, the tank suddenly 'pancaked' out. I guess 15 PSI was too much pressure.

First thoughts were, "there goes $700". The next thought was, "that was a really bone-head maneuver. I should have run bracing wire between the mounting studs." Careful work for the next three hours brought the tank back into shape, and it actually looks OK. Only paint damage from this fiasco is on the underside where I beat the valley back into shape. On the plus side, no more leaks, the rear lip no longer rubs on the frame, there's more clearance for the head steady, and the tank now holds almost 3-1/2 gallons!

I'll mask the tank where the pinstripe would go, respray the top, apply the stripe, and clear everything.
 
15 psi doesn't seen that much. I wonder if an original tank could hold up to more pressure? Maybe the sheet metal on the repops is thinner than stock.
 
If you look at the tank shape, its almost like a saddlebag, U-shaped. Perhaps the metal on the bottom where it rests on the frame, is a little thin, allowing it to balloon.

I was also relying on the pressure regulator on my little, 30-year-old compressor. Maybe it was a little more than 15 PSI. Regardless, it was my fault all the way.
 
Small pressure can cause huge forces when subjected to even modestly large areas. For instance, 15 psi acting on a 12" by 8" panel produces a force of 1,440 pounds!
 
finding the leak on the filler neck in the first place???

Bill T -

I also have a nagging annoying problem with gas seeping out around the filler neck. I replaced the rubber gasket and it made no difference, so i am pretty sure it is the neck.

How did you find the crack/hole where the gas was leaking in order to solder it?

did you also use air pressure? or did you have another trick.

I am getting real tired of this and want to fix mine.

Thanks.
 
Keith, is your leak with an original cap or a modern Andover one ? I bought a new cap a couple of years back because the old one was looking a bit dull and I just couldn't get it to seal properly. Went back to the OE cap and no problems anymore.
 
When I first got this tank, I filled it with water to check for leaks and everything appeared fine. Once I painted it, mounted it on the bike, and filled it with gas, I noticed weeping down the right side. I tried replacing the cap with the original cap - no difference. I tried replacing the gasket with a thicker rubber gasket - no difference. I tried a silicone gasket - no difference.
When I used a rubber sink stopper (the old style with the chain on it) modified to fit under the cap and the cap with a silicone gasket, I knew it wasn't the cap that was leaking.
The tank has about a 1/4" lip around the hole, and the filler neck slips into this lip, giving a good metal-to-metal area to solder or braze from the underside. Its a real pain to get at from the top, but if you clean and flux it really good, you can get silver solder to wick into the joint by heating the filler neck. I found two areas that leaked air, about an inch away from the hinge on each side. Took three tries to finally get the one sealed (that's when I pumped the pressure up, to make sure it was airtight).

To pressurize the tank, I used a plumber's test plug in the filler neck, inserted the fuel taps, and screwed my air hose to one tap (1/4 PT). Open the tap to pressurize the tank, spray soap around the neck and look for bubbles, open the other tap to release pressure, repeat until all holes are sealed.

If I ever do this again, I will brace the mounting studs to prevent pancaking.
 
This idea was on one of the other forums.... No need for a compressor. Seal it up and put it in the bathtub with you. The hot water expands the air and sufficiently pressurizes the tank to see the air bubbles coming out. Yes I tried it - It worked but I had some explainin' to do with my wife.

Yes, 5 lbs would have been plenty so you live and learn.

Russ
 
hi all the best thing for detecting leaks is parrafin even on valve seats if it will hold back parrafin it will hold anything
 
chris plant said:
hi all the best thing for detecting leaks is parrafin even on valve seats if it will hold back parrafin it will hold anything
Click to expand...

care to elaborate on this, i'm not sure i understand.
 
GavinJuice said:
chris plant said:
hi all the best thing for detecting leaks is parrafin even on valve seats if it will hold back parrafin it will hold anything
Click to expand...

care to elaborate on this, i'm not sure i understand.
Click to expand...

I think in the UK, parafin = gas Gas will seep in the smallest cracks

Jean
 
Well last night while in the bath tub with my tank the wife walks in and totally freaks out!!! She thinks I have gone CRAZY. I tried to tell her I was just checking for leaks, She's not buying any of it and tells me to get out of the tub. Before I can get dried off and the tank dried she comes back in and takes a video of me with the tank. Now she says its going on youtube with the question is my husband crazy? What should I do now? I am very concerned, Chuck. Oh and by the way I never saw them making the tanks in the video? LOL LOL. :roll: :roll: :roll: :roll:
 
I think that they do their apprenticeship on the Norton fuel tanks, and then when they are fully competent move onto making the guns. :lol: :lol: :lol:

That would explain the leak. :lol:
 
Actually paraffin is kerosene here isn't it? That's what we used to test valve seal up in Maine, home heating oil would do in a pinch.
 
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