Topic: Exhaust Pipe Dent Removal

[FeralBoy]

I have a lower right exhaust pipe that has a dent at the neck (see attaced pictures).  Outside of that, it is in excellent condition.  Can anybody recommend any services that might be able to repair this for me?  All help appreciated.  Thanks.

[lone*X]

Ouch! Big dent.  Problem you will run into with trying to get that out is that the factory header pipes are double walled to cut down on the chrome turning blue from heat.  It is also fairly heavy gauge.  Doubt the paintless dent removal guys would even try do anything with that due to the double wall pipe.

[Terry in Australia]

No offence to Don, but in fact, CB750 headers are not "double walled". I restored a CB750 K2 built mostly from Ebay and Swap Meet parts that I scrounged up, which included a good set of 4 into 4 pipes, one of which had a badly damaged header that was not only dented, but the damage had also warped the pipe.

I already had several complete pipes and even some spare headers, so I lopped the damaged header off the otherwise excellent muffler, and, using the bike as a "jig" mated one of my good headers to the good muffler, and just mig welded them together. The weld was only around 1/4" wide, so with some silver paint applied, it wasn't even noticeable under the engine. Cheers, Terry.

 

[lone*X]

No offense taken Terry.  I stand corrected.   I was thinking I had read that the 750 was double walled.  One of those thing you think you know that you don't. 

[Terry in Australia]

No worries Don, and many Honda headers were double walled, the headers on my little CX500 certainly are. Cheers, Terry. 

[XLerate]

Right off hand I don't know of any method to fix it that won't leave some obvious tracks. If it wasn't right beyond the apex of bends, no problem. As it is there's no way I can see to drive anything down the pipe because of the curve. Something on a strong flexible shaft, maybe?

One way is to weld studs to various places on dent, starting at deepest, heat pipe red and pull studs to pull dent. Going progressively and manipulating the metal you may be able to get it looking much better or at least more functional. Problem is cutting and grinding the studs off afterwards and the damage that will do, plus discoloration.

Possible to cut pipe as mentioned above, straighten or replace dented section, reweld. Me, I'd try to force a mandrel of some sort down the pipe to press dent out from inside. How, and what to use as a mandrel and flexible driving shaft, I don't really know....

May be easiest and cheapest to just search out some rusted up bike pipe, cut and weld in a good section?

[XLerate]

Another thought: get a solid billet like steel shafting, just a short piece of 2"-3", that's slightly smaller [maybe 1/8" or so smaller?] O.D. than I.D. of pipe. Round one end of it with your grinder. On the flat end weld on a solid steel shaft at least 3/8" diameter, drilling a hole in flat face first then deep weld the shaft into it. Heat shaft to cherry red, put a slight bend in it like for a 6" radius bend. While cherry red dip it in a coffee can or larger container full of old or new oil, to case harden it. Use this as a driver, hammering on end of shaft, to press out dent. As you get deeper, re-bend the shaft to tighter curve. Not sure you could ever get all the way down, you'll have to eyeball that before you even start. I can't see it clearly from here, you'll know if it's possible with pipe sitting in front of you....?

[iron_worker]

I think cutting the entire header section off and rewelding on a new one is likely your best bet if you don't want to rechrome or just replace the whole thing. As was said you could cover the weld with some silver paint and it wouldn't be that noticeable  ... especially if it's the inside pipe.

You could try creating a curved tool to try and drive the dent out (like XLerate mentioned) from the inside but I don't think you'd be able to get much force on the end of the tool with the curve in it.

IW

[FeralBoy]

I appreciate all your replies, but what I am trying to find out is if there is a service that anybody has used or can recommend that can possibly fix this pipe -- I do not have the skills / tools to attempt this myself. 

There are two services I found websites for, but I don't know anything about them.  Here are the two I found, but they look to be more in the dirt bike market, but I assume pipe repair should be pretty standard.

http://www.fusiononeusa.com/index.html

http://motocrosspiperepair.com/Howtopay.html

[ekpent]

Motocross bikes are all about saving weight and who can be the lightest.The pipes I am sure are not as thick and beefy as a stock CB750 header pipe section. Did not read their adds,did they mention anything about vintage street bikes ?

[nancy]

No offence to Don, but in fact, CB750 headers are not "double walled". I restored a CB750 K2 built mostly from Ebay and Swap Meet parts that I scrounged up, which included a good set of 4 into 4 pipes, one of which had a badly damaged header that was not only dented, but the damage had also warped the pipe.

I already had several complete pipes and even some spare headers, so I lopped the damaged header off the otherwise excellent muffler, and, using the bike as a "jig" mated one of my good headers to the good muffler, and just mig welded them together. The weld was only around 1/4" wide, so with some silver paint applied, it wasn't even noticeable under the engine. Cheers, Terry.

 

Terry - hate to fuel the Aussie ego :: )  - but heck - that bike looks just ...perfect. 
Mark

[Terry in Australia]

Thanks Mark, it won BOTM that month, which was nice, and then I sold it to another Mark, and he likes it too. Cheers, Terry. 

[greenjeans]

Jeees - for $50 bucks, I'd let those motocross boys take a crack at it.   Seems too good to be true, but you never know.

Other than that,  A nice header welded in place of the old one can be done pretty easily and will barely be noticeable.

Use the factory silver/grey and it will look like it came from the factory like that...

[FeralBoy]

I sent the pictures to both companies asking if they would do the work knowing there are no guarantees.  If either of them say they will give it a shot I will send it off and post the results here. 

[Rigid]

No, they won't fix it, metal is stretched chrome is damaged, junk.  There, a definitive answer. 

[lucky]

No worries Don, and many Honda headers were double walled, the headers on my little CX500 certainly are. Cheers, Terry. 

The CL350 exhaust were double walled.
The reason Honda double walled those exhausts was for the American market.
The consumer did not think they were large enough even though the tube matched the exhaust port.
That is the reason the exhausts weighed 33 lbs.!

If you do not believe me go through some back issues of the motorcycle magazines.

The CB350 had down swept exhausts unlike the CL350 and had 3 more HP as a result.