Custom Fighters - Custom Streetfighter Motorcycle Forum banner
1 - 20 of 27 Posts

·
Swamp Witch
Joined
·
6,239 Posts
Discussion Starter · #1 ·
Someone posted this to the CB125 discussion group I'm on:
I just thought I would pass along a success story to everyone.

I have a '74 XL125 that has the downpipe exhaust that runs under the engine. Of course, it had multiple dents from rocks, trees and other obstacles encountered by the PO. The expansion chamber has long been rusted off, so basically it is a head pipe that runs to the back of the engine.

One of my friends said you could get the dents out by putting plumbers rubber stoppers in each end, fixing a tire inflation valve into the stopper, and using a compressor to pressurize the air in the headpipe and then using a torch to heat the metal and it would pop right out. He said some blokes used the same process to get rid of dents in gas tanks.

To me that seemed like a lot of work. So the night before last night I filled my headpipe with water, propped it up so that the water was in the section with the dents and let it sit overnight outside. The low was around 20 degrees last night, so this morning it was froze solid and most of the dents were gone. Pushing my luck, I let the pipe thaw in my utility sink during the day and refilled it with water last night and set it outside again. This morning, all of the dents were gone! I REALLY wished I would have taken "before" pictures so I could show you the "after" pictures. Oh well.

Now I have an unobstructed flow head pipe that I can attach a collar to so I can clamp on my supertrapp muffler.

I LOVE IT when a plan comes together!

NOTE: This process might not work on thin wall exhaust tubing and could cause a seam to split, so be forewarned.
 

·
Swamp Witch
Joined
·
6,239 Posts
Discussion Starter · #4 ·
hahaha nice find. of course that would only work a couple of days a year in GA, like this past monday and tuesday
Or you could find a big freezer :)
 

·
Swamp Witch
Joined
·
6,239 Posts
Discussion Starter · #5 ·
Spot heating a pressurized container with an oa torch?

Darwin. Was. Right.

Using water to press or form things wether it be fluid under high pressure or ice is common. Youtube hydroforming. :)
Yeah I know about hydroforming. I guess we can call this the poor man's hydroforming ;)
 

·
Saber Fever
Joined
·
79 Posts
Thanks for the info. I have to try this on my header pipe. It's got a 1/2" deep dent in it. We'll see if I can ever get off the nuts. I broke a stud on the other side.

I'll take a b-a picture when I try it.

Chad
 

·
Member
Joined
·
607 Posts
...how are you going to cap the ends?

Plus, a headers usually have a pretty thick wall. I'm not sure if it'll have that kind of pressure upon freezing.
Ice can be a b*tch for sure. If the ends are plugged well I could see the ice easily pushing it out. However I'd be worried it push more areas as well. But it's a spare header so lets see this!

Ice will get under concrete slabs and raise them inches if not more so it'll work on the pipe. Just hopefully the dent and nothing else.
 

·
lb/hp is what it's about!
Joined
·
10,448 Posts
I've done this to some intake runners found on Chevys TPI engine. Made $85 so far by doing this to those runners.
 

·
Ridin' Dirty
Joined
·
6,773 Posts
Spot heating a pressurized container with an oa torch?

Darwin. Was. Right.

Using water to press or form things wether it be fluid under high pressure or ice is common. Youtube hydroforming. :)
I'm surprised you think this is a bad idea, this is done all the time with 2t expansion chambers.


I'm actually thinking about trying it myself.
 

·
Candy Paint Whore
Joined
·
908 Posts
I bought a beat up Akrapovic system cheap on ebay thinking I could fix the dents with the freezer trick. Astonishingly, the damage was so much less extensive than it looked in the pics I decided not to bother :tongue:
 
1 - 20 of 27 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top