Soldering fuel tank patch

I have a "classic" japanese motorbike which has been recovered from a damp barn after 10 years.

Main obvious problem was the fuel tap had been left on and the carb float needles gummed shut. Having part filled it with fuel, taken it for MOT and failed on rusty fork stanchions and sticky brakes which I have fixed I now find two small petrol leaks from the fuel tank.

Someone has plainly tried to fix this in the past as there is lots of what looks like polyester resin littering the tank. I have shaken an old chain about to break up most of the plastic but it precludes attempting a repair from inside with the likes of POR15.

So I have decided to attempt to solder a repair and then float a piece of brass or copper plate over the repairs.

I don't want to use a flame to avoid damaging the paint work or distortion, does anyone think a 400W electric soldering iron will have enough power? I ask because I will have to buy one or a big lump of copper to heat up.

Any other tips, like what solder (I have some old 60/40) or flux might be best.

AJH

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Problem is, how good is the rest of the tank. it could be rusty all over the place. If you fix one hole there could be another one almost through already. Brian

Reply to
Brian Gaff

Why do you think POR15 or similar wont work? I have used "Frosts Tank slop" which I believe is the same thing in a Land rover tank a SPO had attempted to seal with something else. I used the chain method along with some brick cleaner to clean it out and it remained leak free for the ten years I kept the vehicle.

Mike

Reply to
Muddymike

Mainly because of the poorly adhering resin already in the tank. I don't preclude the idea.

When you used brick acid did it not react with the steel? I have tried citric acid so far and an attempting to get the broken pieces of resin out.

I too have successfully used POR15 on my 101 tank, I first heated it to separate the solder holding the carrier from the tank, cleaned the inside with the cleaner from the POR15 kit, wired brushed back to steel and then brazed obvious holes and applied a thin fibreglass scrim and epoxy which also glued it to the carrier. I then treated it with the POR15 and it held up till I sold the LR. It was quite expensive though, which is why I thought solder may be better and cheaper.

AJH

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That's a risk but from what I can see the rest of the inside looks clean steel, both rust perforations are in a similar position near seams at the rear of the tank on each side. My guess is that moisture accumulated in that part of the tank and rotted through.

AJH

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Personally I'd start from a POV that it won't work :(

As for using a flame, ISTR that any welding on a fuel tank should be performed after it's been steam cleaned for a *long* time.

Reply to
Jethro_uk

Brick acid works to derust steel. It will attack steel, but by the time the rust is gone and you take it out there isn't a noticeable amount of attack. Leave it longer at your peril.

NT

Reply to
tabbypurr

Hydrochloric acid brick acid) will react with the steel but slowly compared with the rust areas. Brick acid is about 30% concentration which is enough to produce nasty fumes and de rust within minutes. Pickling acid used by metal finishers is usually hydrochloric acid at about 15% concentration and about 20 mins pickling time. This will remove rust but cause very little loss of good steel. However, pickling leaves the steel surface very active and prone to surface rusting. Phosphoric acid takes much longer but leaves a non-reacting surface.

You don't want to use acid pickling if the inside surface still has resin remains as the acid won't remove them but may track underneath and cause further corrosion.

I've seen flame brazing and silver soldering of old motorcycle tanks done with minimal damage to paintwork by draping the tank other than in the work area in wet towels and quickly using an oxyacetylene flame in the small area to be repaired. That was, however, done by a very skilled welder.

(I've also watched, from a distance, as a similar repair was carried out on an old BSA tank in the "Yang Po Motor manufactury and construction workshop", a small tin hut in Jurong. When it was suggested we would leave the bike for a day to allow them to vent the tank the cheerful mechanic said "no need" , carefully put out his cigarette and attacked the leaking tank still on the bike with an oxy acetylene flame - which was why we ran some distance. The photo I took (from said distance) shows him happily welding away as a plume of petrol vapour screamed from the small vent in the fuel filler cap. To my surprise not only did he survive but the tank (still on the bike) was neatly welded.) I wouldn't suggest doing this.

Reply to
Peter Parry

As the I can feel the broken remains of resin in the seams through the level sender hole I realise I cannot get the resin out of the narrow sections, also as the tank leaks the resin may have been effective once but has failed.

This is another reason for attempting an external repair.

If I can successfully tin the 2 small areas of steel with the holes in them I will be able to solder a preformed bit of copper over it.

So back to the soldering iron question...

AJH

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Have you tried whacking the outside where the resin is with a rubber hammer? That might be enough to get it to flake off without causing much damage.

Reply to
Rob Morley

you can get a remover for that, personally never used it but told it does work

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Reply to
Mark

This is a method I have heard of: Place abrasive in tank, 30%--50% full. Use grit 1-2mm, Spax screws, broken glass, ... plus 0.5 - 1 liter petroleum. Wedge tank in cement mixer with pillows. Let run 30 to 90 minutes.

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Thomas Prufer

Reply to
Thomas Prufer

Pour into cocktail glasses with salted rim, and add sparkler?

Reply to
Andy Burns

Thanks, that looks interesting and doable if the solder method doesn't work.

AJH

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I've got most of it out but I don't think anything mechanical will get it out of the narrow sections and seams.

Useful to know but a bit expensive.

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Hmmmh. "Molotov Cocktail"? "Rusty Nail"? "Car bomb"? or something for Pterry's trolls?

Thomas Prufer

Reply to
Thomas Prufer

yes but if you dont remove the residue of the lining it will continue to melt/ disintegrate and start blocking your fuel system

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Reply to
Mark

It almost certainly won't melt as it is immune to petrol, there are filters on the fuel tap so I'll keep an eye on them.

In the meanwhile I have soldered the two holes, adding a plate didn't seem to work so I am relying on the solder alone.

I borrowed and old copper soldering iron heated separately with a blow torch.

AJH

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news

ROFLMAO!

so is a 5 lire plastic fuel can.

That melts

Reply to
The Natural Philosopher

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