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Hey, I have a 76 BMW Rbike with a big dent in the front right of the tank. Its not one nice round dent, its more of a crunch about an inch deep at the deepest. Im trying to restore the bike and cant figure out how to get the dent out. Any ideas?

Thnaks

That's a tough one ... My bike has the same problem at the moment, but I just threw a "Preservation paint job" on it and let it be.

Is there a bike graveyard nearby that might have a used replacement tank? A body shop might have some better suggestions (Or one of the workers may be able to fix it for a few $ in his spare time.)

Dents in tanks are never fun. But if your tank is not rotted out you have a good chance of fixing it by

1- remove all fuel in tank.
2- allow to sit for at least one day with the cap off
so excessive vapors can escape.
3- remove petcock.
4- Using an air compressor w/air nozzle attached
and gas cap reinstalled blow air into the petcock
hole the air should expand the tank popping out t
he dents.

Any dents not remover by this method and can't be reached through gas cap with a "WOODEN" dowel should be fudged.

I fix a lot of bike gas tanks. I work in a auto body shop and have a stud welder that welds little nail like studs to metal that you pull on to remove dents. Find a body shop that has a stud welder, Grind the paint off the dented areas. Flush the tank several times with water.FILL THE TANK WITH WATER and weld studs in dents. Pull dents out as far as possible, cut studs off and finish with body filler, prime and paint. Just be sure that you have your TANK FULL OF WATER WHEN YOU WELD THE STUDS ON. After you fix your dents and are ready to go back with the tank flush it good with alcahol to get the water out. Max

madmax wrote:I fix a lot of bike gas tanks. I work in a auto body shop and have a stud welder that welds little nail like studs to metal that you pull on to remove dents. Find a body shop that has a stud welder, Grind the paint off the dented areas. Flush the tank several times with water.FILL THE TANK WITH WATER and weld studs in dents. Pull dents out as far as possible, cut studs off and finish with body filler, prime and paint. Just be sure that you have your TANK FULL OF WATER WHEN YOU WELD THE STUDS ON. After you fix your dents and are ready to go back with the tank flush it good with alcahol to get the water out. Max

That sounds like a man who knows what he's doing.

I would be really leery of the air pressure solution that was offered. While it sounds good you best realize that compressed air can be really dangerous and attempting this could easily exceed the pressure that the tank can handle. If it blows you can expect some serious consequences which could result in loss of limb or life.

Use the stud welder. Take it to a body shop and get them to pull the dent then finish it yourself. That is the proper and safest solution.

Quick 350 wrote:Dents in tanks are never fun. But if your tank is not rotted out you have a good chance of fixing it by
...
4- Using an air compressor w/air nozzle attached
and gas cap reinstalled blow air into the petcock
hole the air should expand the tank popping out t
he dents.

I wouldn't do this. If the tank is old and has some rust in a seam it could pop you could give yourself a nice hole in the old abdomen. Life threatening hole too!. Is this just an idea or has anyone ever actually tried it? I would think that if the tank held the pressure you might actually change the shape of the tank rendering it useless. Please don't try the air pressure method!

The welded stud method that madmax describes is exactly what a reputable body mechanic would do.

JJ

Aside from pressuring up an non-pressure rated vessel like a gas tank (bad medicine, Whiteman), the dent would have to be a very gentle and large indentation for the air to push it out. If the dent has sharp creases along the outside dent line, the metal will work to prevent the dent from popping out.

If you cant pull the dent out you could always fill over it so it looks alright, but you loose that bit of fuel capacity.

my bike i bought used has a dent on the top left side of the tank from the original owner, its a nice rounded smooth dent the paint is fully intact. you really cant tell its there unless your looking for it, although its bout 3 inches wide maybe half inch deep. i want to fix it but... its not hurting anything as it is so i keep putting it off as its on cosmetic. but would a dent like that be an easy fix?