A couple of tank repairs...

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Prof
Founder, Choppers Australia
Posts: 5622
Joined: Sat Oct 22, 2005 3:54 pm
Location: Willunga, South Australia
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A couple of tank repairs...

Post by Prof » Sat Jan 21, 2017 10:01 pm

We had a job today that might interest you.

Mark's VF750 auxiliary tank sprang a leak. They have completely rebuilt the bike and discovered the aux tank had been patched in a previous life but had sprung another leak. So dodging al the Tour Down Under traffic and roadblocks, he brought it down for some TLC.

Prior to cutting (sparks ignite fuel vapour) we washed out the tank and then blew it out with compressed air until virtually all smell had gone. If you don't do this you might discover if God is real or not very violently! On large complex tanks I sometimes run my shovel exhaust into it by a hose with the bike idling. Keeps all the oxygen out and prevents ignition. It is surprising how much fuel vapour can be released from seams.

As a final safety measure, before cutting I put the tank behind my steel workshop door and play a flame into it. No bang means we can get on with the next stage.

Which is to get the tank onto the wire wheel and see just what we have to deal with... and discovered paint and resin hid many little surprises. Arrows show some of the pin holes...
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Previous bronze job and more holes...
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The original tank has a mesh cover on the inside of the outlet tube. This turned out to be rotted out and the whole bottom needs replacing anyway, so I proposed we use a Triumph tap which has an inbuilt filter. Red arrow shows the 1/4BSP bung I machined up so the tap can screw into the bottom of the tank...
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Bottom of tank is cut out with an angle grinder keeping the cuts as straight as possible. It's easier to make the new bottom if the lines are straight. Sheet of 1.2mm steel partly cut to fit. Always start with the most complex part of the patch...
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Fine tuning for close fit is done with angle grinder and linishing belt...
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Bend is done in the vice (see other posts on chain guard bending). X marks the centre of the new outlet...
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Fitting almost completed...
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Hole (16mm) is cut with a step drill in the bench drill. Metal to be drilled is rested on a piece of wood and held with a pliers... never your hand as you will be able to watch some interesting repair surgery at the local hospital if the bit catches and slices the metal through your hand and fingers. Red arrow shows edge of the wooden block...
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All the matching cut areas are steel welded. This last section needs some slight folding which is best done once everything else is welded...
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Bung bronzed in....
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Another view of the finished job. We poured some metho into the tank as a test and got one tiny weep. I didn't bother to repair it as the tank needs to be treated with a tank sealer anyway. A couple of brands of sealer are POR15 and KBS the latter quite a bit cheaper. This tank has a lot of surface rust so needs to have the KBS cleaner and primer as well as the sealer coat.
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Whole job including machining the bung took 2 and three quarter hours.

A couple of weeks ago Dave, and entrant in the Sellicks Races in February this year needed a couple of jobs done. One included his fuel tank. Pics coming...
Chopit'nrideit... Prof

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