Question for old farts

[jrt]

OK, so this is a little off Guzzi topic, but it is a technical question that British old bike owners might know an answer for.

I have this little Kawasaki Ninja 250 that has a steel gas tank. Unbeknownst to me the PFO or FPO or whatever the asshat who had it before me is called, put a pinhole in the tank and tried to repair it with (I think) JB weld. They did a piss poor job, but at least it was so bad a job that the epoxy didn't stick to the tank. So, I have a tank with a pinhole. What are acceptable ways to fix this permanantly? I was wondering about just soldering it up with plain solder (tin/lead) or silver solder or just trying to weld it shut on the mig, but it's awfully thin metal. Any suggestions? Yes, I'm purging all the gas vapors out.

[helicopterjim R.I.P.]

If you can find a tinsmith or old fashioned machinist who does proper silver soldering you will be just fine. If the surface is prepped right it will never leak or come loose. You will still need to purge the tank of fumes but that is easily done with the exhaust pipe of your V11.

[droydx]

OK, so this is a little off Guzzi topic, but it is a technical question that British old bike owners might know an answer for.

I have this little Kawasaki Ninja 250 that has a steel gas tank. Unbeknownst to me the PFO or FPO or whatever the asshat who had it before me is called, put a pinhole in the tank and tried to repair it with (I think) JB weld. They did a piss poor job, but at least it was so bad a job that the epoxy didn't stick to the tank. So, I have a tank with a pinhole. What are acceptable ways to fix this permanantly? I was wondering about just soldering it up with plain solder (tin/lead) or silver solder or just trying to weld it shut on the mig, but it's awfully thin metal. Any suggestions? Yes, I'm purging all the gas vapors out.

 

I've brazed up pin holes and cracks in tanks on several occasions. If the tank is cruddy, you can add "Creme" tank liner, a latex goo that seals smallcracks and rust patches....dont do this unless you need to, because it's a real mess.

[Dan M]

OK, so this is a little off Guzzi topic, but it is a technical question that British old bike owners might know an answer for.

I have this little Kawasaki Ninja 250 that has a steel gas tank. Unbeknownst to me the PFO or FPO or whatever the asshat who had it before me is called, put a pinhole in the tank and tried to repair it with (I think) JB weld. They did a piss poor job, but at least it was so bad a job that the epoxy didn't stick to the tank. So, I have a tank with a pinhole. What are acceptable ways to fix this permanantly? I was wondering about just soldering it up with plain solder (tin/lead) or silver solder or just trying to weld it shut on the mig, but it's awfully thin metal. Any suggestions? Yes, I'm purging all the gas vapors out.

 

 

Soldering is good but be careful, those fumes tend to hang around and you may end up with a different shaped tank!

I've used this product on two tanks with absolutely excellent results. It has been in the tank of my Norton for 11 years now.

 

http://www.por15.com/PRODUCTS/COMPLETEKITS...62/Default.aspx

[badmotogoozer]

If just a pin hole, definitely silversolder. Follow that up with the Bill Hirsch m/c gas tank sealer kit. If the pinhole is from rust, there'll be more on the way but the Hirsch stuff will fix it permanently. Been using it for over a decade with excellent results in both fiberglass and steel. Same stuff they use for aircraft tanks.

 

Sealed up a very bad Duc 750 tank this way. Rust pin holes all along the bottom.

 

cheers,

 

Rj

[Guest Gary Cheek]

If just a pin hole, definitely silversolder. Follow that up with the Bill Hirsch m/c gas tank sealer kit. If the pinhole is from rust, there'll be more on the way but the Hirsch stuff will fix it permanently. Been using it for over a decade with excellent results in both fiberglass and steel. Same stuff they use for aircraft tanks.

 

Sealed up a very bad Duc 750 tank this way. Rust pin holes all along the bottom.

 

cheers,

 

Rj

 

Brazing is prefrrable to silver solder. BUT! These old tanks are very hard to purge safely! I have had a BSA tank that was flushed for two hours with soapy water belch huge flame when a torch was brought near.

Be very careful. If you soft, lead tin solder you should "prick" punch the hole , lightly with a sharp punch to create a slight depression. this will leave enough solder to bond while also leaving enough to allow proper metal finishing to the surface. Even with brazing a little punch is in order.

[Zoom Zoom]

I used to know of a couple of shops that was willing to fix holes in tanks. What they did was to pressurize the tank with an air hose, ie: a constant supply of air that is then escaping out the offending hole. the vapors would then be forced out to burn up in the torch flame. No, I never attempted this myself. For the cost, I was more than happy to pay this guy to do it.

 

Zoom Zoom,

John Henry

[jrt]

Thanks guys. It's not rusty, so I fortunately don't have to deal with that. It looks like someone took a nail to it, so there is already an indentation at the hole. That's a good tip, though. I'll remember it.

 

Dan, Gary- thanks for the warning. I'll be real careful with it.

[BrianG]

Was the tank out with VERY soapy water, and then rinse it out a few times. Take it to your welder and have him flood the interior of the tank with the Argon or CO2 gas from his MIG or TIG machine, and then close up the gas cap. Brazing is likely the best idea.

 

Be aware that "pin hole" leaks along any low-point on the gas tank, (especially at a seam or fold) is an indication of an internal rust issue, and a precursor to more of the same......

 

Every bike with a metal tank should have 1/2 a can of gasline antifreeze (methanol) run through it every year at the end of the season.

[badmotogoozer]

Brazing is prefrrable to silver solder.

 

True, but brazing requires a lot more heat - nearly red hot. When I've brazed tanks more often than not, I get some "sag" in the metal around the repair. Maybe someone who is better at it might have more success... I'm not bad, but there are always people who are better...

 

I always have good success with silver soldering. Never had to use any filler.

 

cheers,

 

Rj

[Guest Gary Cheek]

True, but brazing requires a lot more heat - nearly red hot. When I've brazed tanks more often than not, I get some "sag" in the metal around the repair. Maybe someone who is better at it might have more success... I'm not bad, but there are always people who are better...

 

I always have good success with silver soldering. Never had to use any filler.

 

cheers,

 

Rj

 

You bet , I should have added a caution about the added heat! The trick is to keep the flame moving and work quickly.

 

As far as filling the tank with inert gas, yes that is how we do it at work. Just set up a flow to keep the tank full. You don't want any pressure in the tank as that will keep the filler from penetrating.

I have heard of the circle track guys hooking a hose up to the tailpipe of a LEAN running car. Never tried it.....never will!

 

I have seen a tank that was "purged" and pretty much turned back into a sheet of flat stock when a flame was applied. Always face the filler neck away from people and NEVER expose the neck to an open flame.

[waspp]

I've had good luck using regular solder, as mentioned above make a slight indentation and prep well. I ususlly fill the tank with water just below the hole and use a propane torch for heat. The water adds a safety factor and disapates surrounding heat on the tank itself, then skim coat with JB weld or fiberglass.

 

waspp

[mike wilson]

I've had good luck using regular solder, as mentioned above make a slight indentation and prep well. I ususlly fill the tank with water just below the hole and use a propane torch for heat. The water adds a safety factor and disapates surrounding heat on the tank itself, then skim coat with JB weld or fiberglass.

waspp

 

That's the technique I have used before. I was going to mention that it's usually just not worth bothering if it's a rust hole, as there are usually millions more of the little bastards waiting to leap forth. Your situation seems different. If you fill the tank with water, block all exits and then turn it so that the hole is uppermost, you should have little difficulty soldering it shut. Use zinc chloride flux, rather than resin.

 

mike

[twhitaker]

32 years ago I fixed a leak in my 350 Honda gas tank using a fiberglass patch kit. The leak looked like a stress crack and I figured heat would just add more stress to it. I used a piece of cotton from an old shirt instead of the fiberglass roving and it held fine for the the 3 years I owned it.

[big J]

You bet , I should have added a caution about the added heat! The trick is to keep the flame moving and work quickly.

 

As far as filling the tank with inert gas, yes that is how we do it at work. Just set up a flow to keep the tank full. You don't want any pressure in the tank as that will keep the filler from penetrating.

I have heard of the circle track guys hooking a hose up to the tailpipe of a LEAN running car. Never tried it.....never will!

 

I have seen a tank that was "purged" and pretty much turned back into a sheet of flat stock when a flame was applied. Always face the filler neck away from people and NEVER expose the neck to an open flame.

 

It works fine,though it can give onlookers a bit of a fright. Tape the hose to the car exhaust,rev it a bit for a minute,then light your torch and put the flame into the neck.You'll probably get a bit of a whooomph,but it's ok after that.

 

Except for the time I did it with a VW camper van tank and blew it 30 yards down the street.Couldnt have been empty after all, I had to weld the seams again,but it must have changed shape,cos it wouldnt fit in the hole in the engine bay after that.