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Post Info TOPIC: Tank problem


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Tank problem
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I have a lovely dent in the right side of my metal tank. Any tips on how to straighten this out???

 

Matthew



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Making tank repairs look right is like black magic but it can be done. Post a picture of the damage when you get a chance. I expect you'll get some useful replies.



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if there is no sharp creases in the dent...

pressurize the tank with air only needs a few psi...




...

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Bikes... 06 TTR250 / 09 XT660R / 1977 Montesa Cota 348 MRR / 1979 Montesa H6 125 Enduro...

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If it's a "gentle" dent then maybe it will come out using one of the cheap eBay pullers as shown in my photo. I think the metal on the 60 year-old BSA C15 tank I tried it on was a tad thicker than it could deal with and I ended up breaking the puller screws that you stick to the tank. Shows how strong the glue is though! But for £2.36 delivered it was worth a try. However, it may well deal with any dents in your normal thinner metalled modern tanks. 

I raised the dent issue on the C15 forum and had a flood of advice including dire warnings on using pressure but take this with a pinch of salt except use really really low pressure! Also, strap around the tank or you will find it will open out (like wings) and no longer fit properly.

Other suggestions I got:

  • due to reforming of the metal the dent is now the strongest part of the tank , stick an old sidestand through the filler and massage from outside of dent towards the centre. stick sidestand in the vice and hold tank with both hands
  • Weld a strong bush into a gas cap. stick this "spoon" trough the gas cap and screw the cap where it sits normally. Build a plate to bolt the tank on and get this plate into the vice. Now you can use the "push tool" from inside. Go from outer circle of the dent ....
  • I’ve got a 1”-1/2 “ ball bearing cut in half and welded to a 3/8” rod bent to fit in tank,never heal off anything only tap gently below the dent to knock out
  • Speaking from Experience, I've found that not many pullers are good enough for petrol tanks. The metal used is usually a lot thicker than that on say, a car door or quarter panel. That added to the fact that you're trying to pull a concave into a convex....it just won't happen
  • I remember one time a girlfriend expressed herself to me by pounding her fist on my Triumph gas tank she made her impression of me clear to me...I used a gas station air hose and a rag stuck in the opening and tapped the air trigger very carefully the dent popped out before I blew a pet**** off or split a seam thank goodness..
  • 1 or 2 psi max for leak testing. Do NOT under any circumstances use pressure to try to remove a dent, the tank will distort before there is any effect on the dent, if you can’t reach the dent with any tool at all then either use one of those glue on dent pullers or else cut an access port in the tunnel and then reweld.
  • You only need a few psi to test a tank & to use pressure to push the dents out is potentially lethal. The glue on dent pullers won't be any good on the thickness of the tanks metal, dents will either need welded studs & slide hammer or access to the inside, I they are shallow just use a good quality filler or lead load them if you can
  • Cut out a circle around the valve stem from an inner tube, seal with a Jubilee clip and pressurise the tank by a bike pump connected to the petrol tap. Put the tank in water and watch for the bubbles..
  • I once used a footpump on a CB750 tank, pumping it by hand, it blew the frame tunnel out and rounded the tank. Beware of putting a tank under pressure, another urban myth from the expert in the pub!!!!!
  • Depending on the dent you could try using a Blood Pressure Cuff. I bought one for $8.00 on eBay and used it to push the dent out of my Honda CB750 tank and I avoided repainting the tank. There are some YouTube videos on it. You roll up the cuff part that goes on your arm and tie it with a rubber band, then stuff it in the tank where the dent is, then squeeze the hand bulb to pressurise the cuff. Won’t work for everything but it saved my ass! I finished off with the rounded end of a broomstick handle, tapping gently around the remaining dent from the inside through the gas cap hole until it could no longer be seen.
  • 2 psi max . I have used a garden hose full of water hung from an upstairs window, but don't recommend it as it was enough pressure to push out some small dents.
    I used to have 2 videos, the first was a numpty trying to weld a leaky tank that jetted across the yard outside his workshop and seriously dented a car. The second was the same guy using an airline on a water filled tank to push out a dent. He thought the 90PSI he used for air tools would be about right - he lost two fingers & spent 3 days in hospital for various injuries & most importantly destroyed a tank
  • you will not push dents out just by pressurising the tank ,the dent is the strongest part, to put pressure in connect up to petrol tap outlet

Dentpuller_kit2.jpg



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Great advice, I will let you know how I get on.

Matthew

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"second was the same guy using an airline on a water filled tank to push out a dent. He thought the 90PSI he used for air tools would be about right - he lost two fingers & spent 3 days in hospital for various injuries & most importantly destroyed a tank"

Love that - the priorities of the classic motorcycle enthusiast. Would it have been worth losing 2 fingers if the dent was fixed?

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