I thought I'd throw this out into the KB since I recently PM'd another member on this.

Re: Dent removal

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Heres a little trick for that dent in the pipe. Fill that area with water. Wrap a towel around the dented area only and sit the whole thing outside in freezing weather, or in the freezer if you have one big enough. Ensure the dent is right in the middle of the water slug. In the morning the dent will be gone. I did this on a relatively thick steel Jardine header for my '79 Yamaha and it worked like a charm!

Thanks for the tip, but I don't fully understand the process you described. When water freezes it expands about 10%. Don't i need to seal the ends of the pipe? When the water freezes on the ends it will plug them enough to hold hundreds or even thousands of pounds of pressure. What does wrapping the towel do? The ends should freeze first but the towel is wrapped around the dented area first to insulate it and ensure that part freezes last. Once the ends freeze the water in the middle will be compressed and pressure will rise enough to push the dent out. If the dent is small enough it should push out all the way on the first try. How much water do I fill the pipes? You have to fill the pipe so there is enough water to build pressure - I'd say at least a foot on each side of the dent. Too much and you *could* possibly split the pipe, so don't go all out the first try. Guys do this on 2 stroke expansion chambers all the time.

 

I've seen this work on two stroke pipes, especially the expansion chambers, but thicker wall four stroke pipes seem to be a little tougher to do.

I had a set of pipes with a dent in one of the downtubes and I tried this method. Didn't work. What I ended up doing is putting rubber stoppers in the ends of the pipes with a bracket to retain them. 5 lbs. nitrogen pressure and then got the dent area cherry red with an oxy/act torch. Dent pushed right out. Try at your own risk. These were black pipes so I just repainted after the repair. It would probably leave a nasty looking burnt spot on unpainted pipes, although you might be able to sand/polish it out.

 

FWIW, the Jardine pipes on my Yamaha are probably 1/16" thick carbon steel and are HEFTY! I couldn't believe it worked as well as it did. You have to use enough water and it's absolutely imperative that the dented area freeze last. I cannot stress this part enough.

The other thing is that almost everyone has access to water and a freezer. Not everyone has access to plugs, pressurized gas, and an oxyacetylene torch.

 

I've tried the freezing water trick more than once on 2 stroke pipes. Usually have pretty good luck. On large dents doing it twice or more produces good results.