On a gas tank?
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Feb. 26, 2009 8:03 a.m. Grtechguy SuperDork
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Feb. 26, 2009 8:09 a.m. stuart in mn Dork
It's difficult to remove dents from motorcycle gas tanks. You'd think the paintless dent repair guys would be able to fix them, but whenever I've checked into it they told me they couldn't do it - the metal is too thick and the access is limited enough that they can't get a good push on the dent from the inside. A body shop would probably use some of those weld-on studs and a slide hammer to get them most of the way out, then finish the job with body filler. On a rare tank, I've seen people cut out the bottom of the tank, hammer it straight and then weld the bottom back in again. For something like the Yamaha in the picture, it's probably easiest to get another tank from a salvage yard.
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Feb. 26, 2009 9:30 a.m. Dr. Hess PowerDork
Welding and Gas Tank don't mix very well. It's been done, and there are a lot of safety tricks involved. Just keep that in mind.
On that tank, BONDO is your best choice, or do like Stu sez and get another one.
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Feb. 26, 2009 9:36 a.m. Wally UltraDork
Do you have a big air compressor?
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Feb. 26, 2009 9:42 a.m. JFX001 HalfDork
Wally wrote:
Do you have a big air compressor?
That's what I was thinking.
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Feb. 26, 2009 10:01 a.m. John Brown MegaDork
Before you add air, sign the Aurora over to me... I just don't want to see it lost when the tank makes a boomy.
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Feb. 26, 2009 10:09 a.m. nickel_dime HalfDork
Shotgun?
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Feb. 26, 2009 10:14 a.m. slantvaliant Reader
Hair spray. Match.
Whooomph!
OK, maybe not such a good idea.
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Feb. 26, 2009 10:21 a.m. Woody Dork
JFX001 wrote:
Wally wrote:
Do you have a big air compressor?
That's what I was thinking.
NO NO NO NO!!!!!
I got away with this mistake once and it still scares me when I think about it.
First of all, it didn't remove the dent. The tank expanded like a pair of lungs filling with air. Had it ever burst, I'm sure that it would have killed me.
When I released the air, pressurized gas vapors blasted out.
Also important to remember is that as pressure increases, so does the temperature, bringing the volatile fuel/air mixture closer to its flash point.
Don't do this.
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Feb. 26, 2009 10:21 a.m. 4cylndrfury Reader
If you live near Ohio, there should be a tire discounters near by, who ( for a meager fee) could try compressing it with nitrogen to pop it out. FWIW, N2 is much less boom-tastic than 02...just my (point)2
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Feb. 26, 2009 10:30 a.m. aircooled Dork
Do as suggested above. Stud puller and body filler. Mig welding nails to it might work also, just be careful, the tanks are pretty thin. That is what I did on mine, came out fine. Just body filler might be fine also. If you don't want a lot of filler it will probably be cheaper / easier to find a better one.
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Feb. 26, 2009 10:41 a.m. Grtechguy SuperDork
John Brown wrote:
Before you add air, sign the Aurora over to me... I just don't want to see it lost when the tank makes a boomy.
lol...
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Feb. 26, 2009 12:11 p.m. Grtechguy SuperDork
making mental thought to keep DD locked up until JB finds his donor........
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Feb. 26, 2009 12:11 p.m. stuart in mn Dork
I tried that compressed air deal once myself, it was even on a Yamaha dirt bike tank....didn't work. I ended up with an inside-out tank.
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Feb. 26, 2009 12:40 p.m. ManofFewWords Reader
it appears that if you cut an access hole in the back of the tank, it would be easy to push out. I assume the tunnel is right there. on a side note, I once placed a deflated basketball in the fender of my old vw. Inflated it to pop out dent. It worked.
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Feb. 26, 2009 2:04 p.m. Jensenman MegaDork
Dirt bike expansion chambers are forever getting dented. I helped fix one this way: plug both ends of the pipe, one plug has an air chuck. We used those rubber expanding freeze plugs and cobbled an air fitting together out of some hollow pipe. Connect this to a regulated air supply (the 'regulated' part is VERY important!) with a quick release and pressurize it to around 5 PSI. Yes, that's five, not fifty. Now heat the dent with a torch, it will have to get pretty hot like nearly cherry red and the dent will ease right on out. Be ready to cut the air pressure immediately since leaving the pressure on it will cause the dent to bulge outward which is worse than dented inward.
We did one CR500 pipe which had a lot of unburnt premix residue in it and the smaller of the plugs (in the stinger) flew across the shop and left a nice ding in the steel. It seems we had created a low power diesel engine.
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Feb. 26, 2009 6:28 p.m. stuart in mn Dork
The problem with trying to use compressed air on a gas tank is that they're not round like an expansion chamber - because they have to fit over the top bar of the frame, they have sort of a U shaped cross section, so when you put the air in the two side want to splay out and the underside pushes out.
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Feb. 26, 2009 6:31 p.m. Jensenman MegaDork
Even if the pressure's low, like we did with the expansion chambers? Reason I ask, I've never tried it on a tank. But I do have a ding in the future Street Tracker tank.
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Feb. 26, 2009 7:01 p.m. Grtechguy SuperDork
The aircompressor thing scares me, I'll be honest.
The ball idea sounds really neat, but this is a 1.2? gallon tank. Don't think I could fit anything in there.
anyone know of a motorcycle salvage yard in West Michigan?
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Feb. 26, 2009 7:16 p.m. Rusnak_322 New Reader
I would look on ebay. I have heard of people using dry ice, but never seen it done. The weld on studs are the best bet. There is no trick to welding on a gas tank, you can fill it with water or purge it with argon if you are worried about fumes.
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Feb. 26, 2009 8:22 p.m. Gary_C New Reader
Speaking as a paint & body guy - the safest, easiest and best bet is using a stud welder and slide hammer. I've done it a heck of a lot of times, with great success. Follow that up with a skim of filler and your preference of primer & paint products and you are back to where you should be. Goes quick too.. after you've done a few dozen.
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Feb. 26, 2009 8:36 p.m. Run_Away New Reader
I've heard filling it with water and sticking it in the freezer for a few days? Same idea as the air pressure but a bit slower and safer...might cause some rust issues though,
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Feb. 26, 2009 11:05 p.m. oldopelguy HalfDork
Why not use the same trick that works so well on car doors: a basketball? Pick up a cheap, small, needle-inflatable ball, like one of those mini basketballs, then deflate it with a needle. In it's deflated state attach a hose to needle and toss everything inside something like an old knee-high tube sock so you can pull it all back out. Insert deflated ball to behind dent, inflate through hose, and you get a nice gradual pressure just behind the dent.
When the dent is out deflate the ball and pull it all back out.
