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Thread: tank dent

  1. #1
    GEEZER lsouth3's Avatar
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    tank dent

    Regarding manybikes posting about the tank dent.

    http://www.bmwmoa.org/forum/showthread.php?t=48419

    It would be interesting to find if pressurizing the tank would push the dent back out.
    The tank would need to be empty, dry and off the bike of course with all the openings closed except the one you use to inject the air pressure.
    Just a thought. Don't blow anything up! OR you could use water pressure maybe?
    Lee - The older I get the better I was
    1994 R1100RSL, Black. 1994 R1100RSL, Silver Pearl and a "new" 2001 R1100RS, Red!
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  2. #2
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    I have also thought about that method.
    However...from what I have read on the net this is a dangerous method with a low success rate.
    Apparently you stand a good chance of ballooning your tank out in all the wrong places. The compressed air exerts pressure evenly and has no idea where the dent it, it is more likely to blow out a seam.
    This is what I have read anyway.
    People who have claimed success say very low pressure, 4-5 psi, is all that is required.
    Last edited by manybikes; 09-24-2010 at 09:14 PM.
    War is when the government tells you who the bad guy is. Revolution is when you decide that for yourself. ÔÇôAuthor unknown

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    Danger Will Robinson Danger - maybe talk to the guys who do paintless dent repair?

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    I'm with you Gerzinam, next week I am taking my GSA in to a PDR shop to see if they can straighten it out.
    War is when the government tells you who the bad guy is. Revolution is when you decide that for yourself. ÔÇôAuthor unknown

  5. #5
    BMW MOV Club Director ENFOMAN's Avatar
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    I have used an over the counter dent repair system that has a plastic handle and hot melt glue. once the glue sets, just pull on the handle where the glue meets the dent and it pulls out. may take a few times, but the repair is invisible. best ten bucks for body work I spent. This worked on a tank and a vehicle. I have not seen them for sale lately though.

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    Hey Infoman

    Yes, the kits are still available on ebay etc.
    Was it a motorcycle tank you fixed? One of the PDR shops I went to said that motorcycle tanks have metal that is too thick to pull with the glue method, others said it will.

    I am taking mine to a shop that feels confident that they will be able to pull the dents, no one will guarantee a perfect fix.
    I don't mind getting my GSA dirty but dents really drive me crazy, most people claim they can't readily see mine but I see the damn things everytime I ride it.
    War is when the government tells you who the bad guy is. Revolution is when you decide that for yourself. ÔÇôAuthor unknown

  7. #7
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    My r1100r's tank was dented by the PO who dropped it against his r100s in the garage. After weighing the cost of repair and repaint, I found a "bagster" tank cover on ebay, and I'm very pleased with the look.
    best regards,
    Mark

  8. #8
    BMW MOV Club Director ENFOMAN's Avatar
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    Yes- It was a spare tank that I got on the cheap because of the dent. I figured for the price, it was worth the try. I too, was skeptical. I had no Problem at all. Of course, I am told it depends on how fresh the dent is. I did not even need to have it repainted. Also worked good for a body side panel, I don't even rember where it was excatly after i pulled it out some time ago!

    Bob

  9. #9
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    Paintless Repair

    Some years ago, I had a crease taken out of a single-wall (important factor) tank for a Honda CB400F. IF the paint "capsule" is not broken, and IF you live in an area that gets a lot of hail (Colorado, etc.) the guys who do this can be VERY skilled. In any light, you could not see any evidence of the crease.

    I also personally watched this repair done to a seriously hail-damaged Acura hood, and you could see NO evidence of the damage when the maestro was finished, and I mean, NONE. [Again, this was in Colorado, where they get a lot of practice.]

    There is a lot more "art" to doing this well versus "science" -- which I guess is true of any wrenching activity, eh? -- so know with whom you are dealing before going this route - experience counts.

    Walking Eagle
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  10. #10
    Benchwrenching PGlaves's Avatar
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    Having not seen the dent in question this is purely a guess based on logic:

    The dent which was caused by negative pressure (vacuum) in the tank probably didn't significantly stretch or kink the metal. And since negative pressure pulled it in I think positive pressure will push it back out. Or the body shop suction cup method?

    This is not in the same category as when impact (falling down) dents a tank where usually the metal is significantly distorted and much harder to straighten.

    I don't think it would take a lot of pressure. Seal the openings: close the lid, clamp off the vent lines and pump pressure line. Attach a cut-off tire stem to the fuel return line by inserting it into the line and using a hose clamp.

    Then take an ordinary bicycle pump and pump a little pressure in there. Not a lot, a little.
    Paul Glaves - "Big Bend", Texas U.S.A
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  11. #11
    Registered User ANDYVH's Avatar
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    Not so sure this would work. I tired it once years ago on a Honda fuel tank, and the air pressure actually caused the whole tank to expand and got wider at the "hump".

    Before appying air pressure, I would go around the tank in at least three places with those small ratchet straps to keep the tank from expanding. Air pressure, as said earlier, is exactly equal everywhere in the tank, so it will expand all the interior surfaces of the tank.

    But maybe with straps around the outside, and a dent puller stuck/glued to the outside of the dent, and air pressure inside, it may pull the dent out.
    Last edited by ANDYVH; 09-26-2010 at 02:40 AM.

  12. #12
    Benchwrenching PGlaves's Avatar
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    Quote Originally Posted by ANDYVH View Post
    Not so sure this would work. I tired it once years ago on a Honda fuel tank, and the air pressure actually caused the whole tank to expand and got wider at the "hump".

    Before appying air pressure, I would go around the tank in at least three places with those small ratchet straps to keep the tan from expanding. Air pressure, as siad earlier, is exactly equal everywhere in the tank, so it will expand all the interior surfaces of the tank.

    But maybe with straps around the outside, and a dent puller stuck/glued to the outside of the dent, and air pressure inside, it may pull the dent out.
    Yes but, so was the vacuum equal over the entire internal surface of the tank and that pulled it in at the least strong area. If vacuum pulled it in, and that is all that caused the dent, then + pressure equal to the - pressure that pulled it in ought to push it back out.

    I agree it probably won't work for a dent put in by a rock or a knee.

    Bicycle pump. Atmosphere + a few p.s.i.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
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  13. #13
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    Does anyone know it the 04 GSA tank is single or double walled?

    I may try and post some photos showing the suction dents. It basically sucked in the tank on each side closest to the seat where the tank curves in.
    Last edited by manybikes; 09-27-2010 at 04:17 AM.
    War is when the government tells you who the bad guy is. Revolution is when you decide that for yourself. ÔÇôAuthor unknown

  14. #14
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    I would think for a double wall tank a dent from negative pressure inside would not appear on the exterior surface.
    Mark

  15. #15
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    I would think for a double wall tank a dent from negative pressure inside would not appear on the exterior surface.
    Mark

    Hmm..never thought about that

    Good point!
    War is when the government tells you who the bad guy is. Revolution is when you decide that for yourself. ÔÇôAuthor unknown

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