Dent repair gas tank

Any ideas as to how to do dent repair on a motorcycle gas tank?

Plastic or metal?

Metal. Steel.

Don't try air - it will blow out the seams.  I have used a stud welder / puller to pull out an inaccessible dent in a tank.  If the dent can be reached through the fuel fill, you may be able to push it out with a dowel or other such device.

water to the top and freeze?

How big is the dent? Pics will help.

wheelsmithy said:

water to the top and freeze?

 

I have done this successfully to tuned exhaust pipes. 

You might try a paintless dent repair shop. Some of the tools they have will reach just about anything to push out a dent. 

On a beater bike I filled a golf ball size dent from a tankslapper with bondo, repainted, and sent it down the road.  Looked good to get it gone.

Dent wizard has some trick spoons just for this.    If its an old school tank with a tunnel for the frame to pass through you have to be carful not to collapse the tunnel with air or water pressure, as well as seems popping.

It's off my 2001 r1200c. In the move, a strap broke and another then loosened up and muy bike "leaned" into my engine hoist. I now have 2 "line" dents about 3" long and ~ 1/8" deep along with scratches. Paint isn't savable, unfortunately. They are towards the back half of the tqank fo not readily accessible from the neck with home tools. I may try paintless dent remover, but I do have a stud gun as well. THis darn move!!

CJ said:

Don't try air - it will blow out the seams. 

I did that once.  I wasn't happy when the tank turned inside out.  

I also talked to a dentless paint repair guy once about fixing a motorcycle tank - the problem is the metal is a lot thicker than your typical car fender, so depending on where the dent is in the tank (and they always seem to be in an inaccessible spot) it may not be possible for them to make the repair.

I would just replace the tank, if its a crease it will never look right without a repaint and at that point a used take-off would probably make more sense.  Ebay has a whole host of them for around $400, you could also try local cycle salvage shops.  If your tank isnt too bad, Keep it on the bike and keep the pristine one for when you sell it or "just in case"

I had a similar incident with my ZX11 and it was far cheaper to just replace the tank than it would have been to get it fixed and redecalled.  

Unfortunately, a r1200c is a rare bird and my color of blue is even more rare. The ivory and black ones are the most common. 

HOw about a grease-gun and a LOT of grease?

Grease gun pressure

Manual Grease Guns. Manual grease guns include lever-action and pistol-grip models. These popular tools are widely used and are the most economical type of grease gun. Manual grease guns can achieve pressures up to 10,000 pounds per square inch (psi), while plug-valve sealant guns can reach 15,000 psi.

The problem with using any type of pressure is it will turn it in to a round ball as it try to equalize the pressure at all points at once. unless you have it in a mold to blow up into.

I'll let you in on a dirty little secret. The tank on the Murdercycle has a bondoed dent. At least 1/4 to 3/8 deep. Way deeper than any recommendation I've ever seen. It has been fine for over 5 years. Sitting in direct sunlight 100 degree days and 20 below winters. I cannot garuntee anything on your end, but you can "fix" this yourself if you have the ability to shrug your shoulders and say, "Berk it!"

In reply to Appleseed :

So if weld on stud pulls don't work, don't sweat it and bondo it?

https://www.youtube.com/watch?v=UB0eRYHtpYo

This might help, he has quite a few videos on the internet so he must be an expert, right?

What's the worst that could happen? The bondo pops out and the tank is still fubar. You got some bodywork practice.

  Sand the dented area down to bare metal, alcohol wipe the area to get rid of any oils and slather in the mud. Maybe do it in 2-3 coats to minimize the heat buildup when it cures. I used actual Bondo brand for a big box store.

If you are going to attempt to rattle can finish it, use paints and primers  from the same brand. If you want it sprayed by a shop, ask them what prep, paint, primers, etc... they would use so they don't have to spend time to undo what you did. 

Everything I've ever read says what I did shouldn't have worked, so your mileage may vary. 

Pro tip: if the dent is along a character line, put masking tape along one side. Bondo as usual. Pull the tape off whole its still soft. Let it harden. Then tape up the line on the bondoed side. Mud the other side, and pull the tape off once you are done spreading. Now you have a nice peak along the line. Sand it back carefully, minimizing passes over the line. Otherwise, a character line ends up way too smooth to match.