Re: [MV] Pinholes in gas tanks

From: GOTAM35 (gotam35@sc.rr.com)
Date: Sun Jun 30 2002 - 06:00:06 PDT


----- Original Message -----
From: "J. Forster"
> I have a small motorcycle gas tank with some pin holes. A pro radiator
shop says
> no can fix. Any reccomendations, other than the obvious about explosion
> hazzards and removing fumes before starting, for soldering the holes up?
> Specifically:
>
> Hard or soft solder or braze?
> Can it be soldered on the outside and be a reliable job?
> Any tips?

I have never tried sealers but they sound like the best alternative.
But incase anyone out there can't find a good sealer
or you have holes to big for it(I'm assuming the sealer would run out of a
quarter sized hole)
or your can't get your tank rust free enough on the inside(I'm assuming lots
of rust would eventually bubble up under the sealer just like it would under
paint
or your like me and too cheap
Here's what I have done on tanks to fix hole big and small:

First: clean the tank inside and out. Make sure all gas is removed and then
fill with water, empty and then sit in the sun for one month (less time if
you feel comfortable).

Next: clean the area on the outside with a wire brush to remove junk in the
depressions. Then clean it with sandpaper. If you don't clean with
sandpaper the solder will not stick. I'm not sure why but that has been my
experience.

Next: stick an air hose in the tank with a small amount of air being
released. This doesn't work as well as nitrogen, but it will keep fumes
from building up. I have make lots of acetylene bombs for fun and explosive
gases have to have just the right Oxygen mix to work. The air will mess
this up. You should have the air hose in loosely. You want air leaking out
around the filler neck. Pressure on the tank will blow the solder out of
the holes. KEEP A FIRE EXTINGUISHER ON HAND. WEAR GOOD SAFELY GLASSES AND
A HOOD IF YOU HAVE ONE (I'm the paranoid type).

Next: rub plenty of flux on the spot to be soldered. Heat the are slowly.
Use a small torch, using a torch too big for the job is the first step
toward failure. If you get it too hot the flux will burn and won't work.
Take 95/5 solder and rub it on the heated area. Don't try to fill the hole
yet. You are trying to ensure the solder has stuck to the surface at this
point. If it has stuck to the surface your in good shape. It is there for
life, unless you burn it in the next step.

Next: if the holes are too big to fill at this point, make a patch. Copper
is the best thing to use. I have used a penny before, but I now try to
uphold the law. You can cut a patch out of a piece of copper tubing. Make
the patch fit the shape of the tank as much as possible and then clean it
really good. Flux and solder the side to be attracted to the tank, and then
set it in place. Gently heat the area melting the solder on the patch and
push it down in place. If you don't need a patch, build up solder on the
area you have prepped and don't over heat. I think it would take a week to
describe the tricky part about heating, so just experiment and learn. If
you get the soldered spot too hot the solder will fall threw the hole.
Apply heat to the tip of the solder too get it melted and in place, then
heat the spot again. If it falls trough with you, do it again and use less
heat.

Be very careful. I hear of people from time to time getting killed cutting
up old fuel tanks for scrap. We don't want this to happen here.

If properly done, a soldered patch like this will hold at lease 100 psi
(I've did this on pressures a lot higher). Soft soldering is cool enough not
to melt a hole in the tank. If you have rust holes the tank is very thin at
the hole and high heat brazing would melt the tank. If any one any questions
feel free to contact me off line. Sorry to use up so much space, but it
would appear everyone is on the way home from Dallas today anyway. Joe
Trapp.



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