Fixing exhaust dent

FLBob · Apr 16, 2002

I know some may think I shouldn't but I have a need to fix this dent myself - FMF kg 35 I think, if it matters. I smashed it pretty good - bike (97 KDX 220) still runs great. I'm planning the compressed air/torch technique. Can someone who's done it give me an idea of the air pressure? I'm thinking 25 to 35 psi. When heating should I start at the center of the dent, the edges, or?

Thanks!

Kawierider · Apr 16, 2002

hey flbob,
I read an article about this in one of the magazines this month...not sure withch one though. It said seal both ends then fill the pipe with around 100lbs of air....then heat the dent...i bet your best bet woudl be jsut ru nthe torhc over the whole dent and try and heat it up evenly.....also they cautioned to keep the pressure below 150 at all costs, so keep an eye one it as you heat it up.....i have never done it, but thats what the mag said.
Tim

jmics19067 · Apr 16, 2002

Do a search on the subject someone had good results using 40 psi after he heated up the entire dent dent. I personally had a plug blow out and will not repair my pipe that way. Just be careful

michigan · Apr 16, 2002

If I recall, that mag said not to exceed 100 psi, but you shouldn't even need that much.

Another idea that might make this a little safer-

If you put 70 psi in a cold pipe then heat it for 10 minutes with a torch, you'll have... a heckova lot more than 70 psi.

So, get that dent red hot, then seal and pressurize.

Jaybird · Apr 16, 2002

Or drill a hole in the opposite side, insert small rod and press dent out, weld up little hole. No danger of mishap.
I wouldn't fix a pipe with pressure on a bet.

SndyRds · Apr 18, 2002

I have done this fix and it can be dangerous. Use only 10 to 20 psi as the heat from the torch will cause expansion of the gasses inside. I heated it up from the outside in using a circular motion. After you capped the ends, wire them on and use hose clamps to hold the wire on. I tried this and the first time I used 40 psi and STILL blew an end cap off. And I was using stainless steel safety wire. I STRONGLY suggest that you wear safety glasses, ear plugs and a face shield. oh and make sure and point the ends of the pipe away from you. Also the places that do this professionally only charge 40 dollars or so and have a fast turnaround. Be aware that if you burn through, you will have hot explosive gasses shooting right at your torch and face. At 10 to 20 psi it will take a little patience, but it will work. Please post and let us know how it came out.

FLBob · Aug 23, 2002

Finally did it. H/S season starts here soon so trying to get ready. Came out just OK - discolored and rough because it was dented at a seam. 25 psi and british red hot - it took less heat than I thought it would. My contraption leaked air, I kept it pressurized with a regulator constsantly attached so the hot gases just escaped thru the leak - boy it made for some stinky smoke.

I'd probably do it again. Now though, while re-installing it I found that it doesn't fit exactly right. If I remember, before the dent, I had to stress the brackets to get it on, so it wasn't perfect then. It seems to be a little worse now. Do the guys that fix dents have a jig or whatever so they can fix any mis-alignment at the same time?

Jaybird · Aug 24, 2002

Originally posted by Jaybird
I wouldn't fix a pipe with pressure on a bet.

demographic · Aug 25, 2002

I remember reading a technique years ago used to make scooter exhausts which was to cut out two sheets of steel, weld them together around the edges, weld on a pipe fitting then pump up with a hand water pump. Now as its only water and does not compress it also will not blow up in your face. When you are done you still have an exhaust that will have all its bends in one plane (like a snake that's lying on a flat surface) and it needs to be cut and the cut areas turned round (if you look at most two smoke pipes you will see that even though they use big dies to stamp them out,or pressure form them into a die the seams don't line up so they are cut and welded in a simillar manner (Errrm I think :think: ). I would say that you could use water pressure to blow out dents in a far safer way then the heat up and close your eyes method :flame: I do know lots of people use air pressure and heat but I am buggered if I would stand next to them while they do it :flame:

demographic · Aug 25, 2002

There is a link to an article about the pump up and heat up method HERE

Fixing exhaust dent

FLBob

Kawierider

jmics19067

michigan

Jaybird

Apprentice Goon

SndyRds

FLBob

Jaybird

Apprentice Goon

demographic

demographic

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