pin hole in fuel tank

[neat street]

Hi All, after a good and succesful clean of the tank on my CB500, I have found a couple of pin holes..... The question is, would you mig weld them, braze, or use lead solder like they used to do on filling body pannels instead of filler years ago? these must have been there for a while as the PO had used some kind on filler on the outside which `done the job`. I dont realy like the idea of using a tank seal as many have had issues with this in the past. I will prsure test the tank to find all leaks :-)

[Johnwebley]

If they are small, use solder

Can't think of any downside



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[McCabe-Thiele (Ted)]

I had a pin hole leak on my Yamaha tank, I tried a tank seal product, that lasted less than a week.
I ended up fitting a new tank.
When I pressed along the underside of the pinholes it was rotted out everywhere.
Clearly it is dangerous to use heat as there is a risk from residual petrol vapour.

I have been told that older bikes have thicker metal, the pin hole is the tip of the Iceberg imho.

[ozzybud]

If you have 2 pin holes you have dozens ready to break through.. A proper application of an Epoxy liner will last for years. The prepping of the tank before application is key. It needs to be free of loose rust and oil or grease.I use acetone as a final rinse. I use a 2 part kit from caswell.

https://paulyaffeoriginals.com/products/caswell-epoxy-tank-liner-kit-clear

[Jond99]

I’ve used POR15 in the past with great success, as above preparation is key. Even though you’ve already cleaned it I would do the process again to ensure you move any rust that may have developed.

I had some POR leftover in the tin and when it’s gone off it’s absolutely rock solid.

For the de rusting process used Flowliner Bio rust instead of the one in POR15’s system.

POR does seal pin holes but depending on where the hole is if needed you could add a bit of structure to held the liner seal with something like JB Weld tankweld. It’s function in this senario is purely to contain the liner whilst it goes off.

[neat street]

Thank you all for your comments, this gives food for thought. each proccess is not easy (maybe the welding is the simplest) the tank is compltetly clean inside from days left in white vinegar, presure washed, then done again, so surpised at the result being so good, this is how I found the leak, over last two days 1/2 a gallon lost. The leak is comming from the back of the tank where the seam is at the `top` underside, I did place some diesel with a small amount of oil to keep away flash rust after the pressure wash, so not too much of a problem to de-grease/clean out the tank again if I decide to use a sealer. I will let you know which way I go and the results. whichever way, everything has to be `very clean` for best results. As you will note, no chance of any fuel vapour issues.

[K2-K6]

Sounds like no real risk in regard to heating it for weld etc.

If itdid have petrol fumes though, just blowing a car exhaust into it effectively neutralize anything of atmospheric nature within to make it safe.

Welding, if it's rusting and thinned out on a plain panel section, usually melting (steel welding) will likely chase out a rabbit warren of holes as it can be very thin, making it "delicate" to control the heat path.

Ordinarily, fuel tanks are leaded to fix the pinholes, this being well bellow the melt heat needs of welding. Usually quite simple with clean surface and decent fluxing. This is ordinarily the least intrusive method of fixing if reasonably available.

[mickwinf]

I had pin holes on my 500, solder works but mine had some holes under the reinforcing plates so not accessable. I used a sealer and seems to be holding up ok a year later.

[neat street]

Thanks again for the up-dates, I think I will try lead first and see how that works, then..... if that fails. :-)

[florence]

I had a pin hole in my tank.  Sadly, when trying to clean it, with a view to soldering, it just got bigger and bigger.  I tried to solder on a patch but it was not successful.  In the end, I had to put on an early 750 tank; it was much too expensive to find a decent 500 or 550 tank.  The old tank is still in my workshop in the 'not sure whether I should throw this out' pile.

[JezzaPeach]

I also used POR15, the tin lid was so stuck I had to rip it off with mole grips. Prep is vital, I got hives from the fumes (on my exposed neck and forearms, went after about 3-4 weeks) so I’d wear a mask, cover up, and have a fan blowing the fumes out of the garage door. That was about 6-7 years ago and the inside of the tank is looking very sound and clean. Didn’t have holes just the start of fine rust. I covered the tap hole with a shaped piece of wood with 2 holes for the bolts and a gasket made from a cycle inner tube.

[neat street]

Well, after alot of tests and trials, I have solved the pin holes. The main issue was to get the solder to stick to the steel, I tried all sorts of solder, mixed led and tin, tin only, acid fluxed core solder, fluxed cored solder... Also a range of fluxes, including an acid to `clean the suface` before using flux (did not work, but if you do this make sure you clean off the acid with plenty of water before fluxing), and in all but one case  which arrived today, was getting balls of solder rolling all over my test piece of mild steel. what I used today was  Eastwoods tinning butter and hey presto, it worked with all the solders that I had. I ended up using the plumbers lead free solder as can be seen in the before and after pics. may not be the prettiest, but have not got any leaks after a presure test. The main trick was to place the tining butter on the fully clean and prepaired surface (Dremmel with small wire brush was my tool of choice to get into all the small areas), heat the surface (I used a gas blow torch) but not to let the surface get too hot, just enough for the solder to melt and flood, taking it away from the surface every so often as needed and re-aply heat as  required just to keep the `tin` molton. Made sure all was sealed and gave a good wipe over to clean (helps to see if any more needs adding before presure test), then a cleaned over with a small power file. Hope this may help a few others with this problem.

[florence]

Well done, looks great.

[Skoti]

Tidy job.
Well done and a useful explanation of your technique for others attempting similar work.

[SumpMagnet]

Great info @neat street
I know lead was effectively used as a filler back in the dim and distant past, but it's not something I have ever tried. Sure, I have soldered wire and copper pipes etc. but I have never tried something like this. Thanks for sharing your tests and results.