Petrol tank leak

stu · May 7, 2022

Hi
I've a very slight weep from the front mounting stud - original 73 roadster steel tank. I'm considering lining the tank and POR15 3 part approach has been recommended for a fix to avoid welding. Anyone tried this stuff ? I'm keen to get the bike back on the road as soon as / uk (scotland) based

concours · May 7, 2022

stu said:
Hi
I've a very slight weep from the front mounting stud - original 73 roadster steel tank. I'm considering lining the tank and POR15 3 part approach has been recommended for a fix to avoid welding. Anyone tried this stuff ? I'm keen to get the bike back on the road as soon as / uk (scotland) based

Please do not line it. Bring it to a talented weldor. No paint will be harmed.

concours · May 7, 2022

I can outline the plan, and the need to: "avoid welding".

maylar · May 7, 2022

Or... JB Weld on the outside?
A MIG bead would be my choice.

MexicoMike · May 7, 2022

We used JB Weld to seal quadrajet carburetor casting plugs, most of which were submerged in gasoline during normal operation so it will work with gasoline BUT it would be best if it could be applied on the inside of the tank. It might work OK on the outside but I'm not so confident. OTOH, what the heck, it can't hurt...

kommando · May 7, 2022

I would only consider welding, the threaded insert gets a stress crack around the penny sized OD. You need to fill the crack with steel, anything weaker will allow the crack to grow in length.

concours · May 7, 2022

kommando said:
I would only consider welding, the threaded insert gets a stress crack around the penny sized OD. You need to fill the crack with steel, anything weaker will allow the crack to grow in length.

This is the right answer. JBWeld is great stuff, but the crack that is leaking was caused by flexure.

concours · May 7, 2022

maylar said:
Or... JB Weld on the outside?
A MIG bead would be my choice.

TIG is best, MIG will work, .023" wire, in the hands of a MASTER.

concours · May 7, 2022

concours said:
I can outline the plan, and the need to: "avoid welding".

A liquid penetrant dye check will show the cracks not visible to the naked eye.

concours · May 7, 2022

robs ss · May 7, 2022

concours said:
TIG is best, MIG will work, .023" wire, in the hands of a MASTER.

Is the tank and boss just mild steel or something more exotic?

concours · May 7, 2022

robs ss said:
Is the tank and boss just mild steel or something more exotic?

garden variety low carbon steel.

rweb · May 7, 2022

Get a washer that will fit over the bung and big enough to cover the crack, you may have to drill out a fender washer, and solder it in place.

Fast Eddie · May 8, 2022

The crack has been caused by stress, stress that caused mild steel to fracture. Fixing it with anything less strong than mild steel means it’s highly likely to fail again. Soon.

Soldering will cause more heat damage to the paint than skilled welding.

I’m with the welders on this one.

Peter R · May 8, 2022

Had a crack at the same spot as the O.P years ago, brourght it to a guy who did many similar repairs.
He used bronze welding to cure the leakage, and it still holds today.
Bronze welding is actually soldering (technlcally speaking)

stu · May 8, 2022

Thanks for the replies - I'll see if I can find a welder (Central Scotland) will tackle this. Out of interest - why do tank liners get a bad press ? Must help stop the rust no ?

Gilesy · May 8, 2022

I agree about the welding but to answer your question I have used Por15 and it worked fine, make sure you stir it. My N15 has had it in for a couple of years without problem. There is an interesting article in Roadholder about tank lining. Good luck.

kommando · May 8, 2022

stu said:
why do tank liners get a bad press ?

If a tank liner goes bad then it comes away in lumps, very difficult to get them out the cap hole or break them up inside so they do. They are definitely needed on fibreglass tanks but on steel tanks you can use phosphoric acid on the cleaned and dried tank to create a rust resistant coating which cannot peel off.

Shelby-Right · May 8, 2022

Fuel tank or oil tank ?, maybe wash tank out a few times with hot soapy water and dry ,you can machine up a washer suitable thickness and diameter 1 1/4 - 1 1/2 and countersink a machine screw into it TIG weld it into washer flush , hacksaw off old stud ,file flat , clean well and JB or loctite weld , its made for metal ,this will work for quite a while ,I think i would prefer a proper steel repair , the oil tank I would just tig around the bung and repaint .

concours · May 8, 2022

Shelby-Right said:
Fuel tank or oil tank ?, maybe wash tank out a few times with hot soapy water and dry ,you can machine up a washer suitable thickness and diameter and countersink a machine screw into it TIG weld it into washer flush , hacksaw off old stud ,file flat , clean well and JB or loctite weld , its made for metal ,this will work for quite a while ,I think i would prefer a proper steel repair , the oil tank I would just tig around the bung and repaint .

OP has a fuel tank issue. I posted a pic of the oil tank cracking, and dye check process, as the failure is similar in nature.

Petrol tank leak

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