Whats the best technique for repairing blow holes ?

[mickyblueeye]

I have a motorbike tank that has had attempts at repair on the bottom. Looks like someone who is used to welding military tanks has had a go with a mig welder! There are several holes and fissures? that need fixing plus some areas have been ground back too much and the base metal is now less than 0.5 mm thick in some places. The tank had been previously modified (by someone who new what they were doing!) to make it fit a custom built frame so is essentially a one off. I would appreciate any advice.

 

[J.B. Welding]

Hi Mick, you can fill holes by tacking around the edges and gradually working your way into the center, but on a fuel tank I would try to plate whatever you can, or even split off the bottom of the tank at the seam and remake the entire piece. It really not worth taking any chances with a repair like this the last thing you want on ur bike is a 'fireball feature'. The less than 0.5mm areas need plating cos of the danger of cracking with vibration. Sorry its not what you want to hear but if your not 100% on this job it might be worth it getting a pro to have a go, specially if you might sell the bike when fixed up. Not worth the risk.

 

[wristpin]

Was watching an old Wheeler Dealers the other evening and they had taken a TR6 fuel tank to a specialist who degassed it, cleaned up the affected area, tinned it and soldered on a patch.

 

[norlander]

don't know if this helps but when I blow a hole or part of the joint away with my lift tig set up (no pedal etc) I pick the next size filler rod up to fill the hole gap, sometimes I have the filler touching the workpiece and I walk the arc on to it and do the edges as JB has described.
I agree with his advising caution as its a fuel tank.
Does the tank have a decent breather? I'd be worried about pressure build up on a hot day if parts of the tank are only 0.5mm (but thats me-I cut iffy tanks in half and mount em on the wall).
Also, the tank has to contain the fuel if the bike goes down or falls over so the job needs to be a good un.
Maybe if you post some pictures the more experienced welders like JB above/hotrodder etc would be more qualified to advise having seen the actual job needed?Good luck.

 

[mickyblueeye]

Thanks for you replies, JB is right, not want to hear but I think cutting the bottom out and remaking is the way to go! The tank was off of a Suzuki GS1000GL shaftie, which are quite rare now so getting another tank is highly unlikely. It has been modified to fit a one off frame and the GRP seat unit moulded to fit as well so I really need to fix it up. Going to knock a template up first in cardboard to see how it looks and I think I might gain a couple of litres capacity! Thanks again, I will let you know how I get on.

 

[Mr shiney]

Braze it. I just repaired similar holes in a Can Am tank doing this.

 

[Rig Pig]

Fill it with hot water & wash it out then solder the holes up