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Discussion Starter #1
Hi all! I hope this is the right area for exhaust questions. I have a 1975 CB200t that's in pretty good shape. Unfortunately, the bike spent most of it's life in California, and the coastal air has caused minor rust spots on most of the chrome. I just noticed that there are several spots that have rusted out on the underside of my scrambler exhaust pipes which it's blowing exhaust out from (holes are about 1" long by 1/4"-1/2" wide). The P.O. also patched a hole toward the front of the pipes. They had some mud dobber welds, but they are fortunately covered by the heat shield shrouds. so I have three questions.

1. Does holes in the exhaust pipes rob performance?
2. What would you guys recommend for repairing these holes?
3. Is there anything else I should do to the exhaust while I have it off the bike for repairs?

I'm a complete noob at motorcycle wrenching, and wasn't sure if the exhaust pipes begin to accumulate black deposits that could restrict air flow.
As of right now, I am thinking of removing the pipes, soaking them in a degreasing/cleaning solution, then soaking them in a rust bath (Metal Rescue) to treat the rust, and then patching the holes with a high heat J-B Weld product (see link)

https://www.amazon.com/J-B-Weld-37901-Temperature-Resistant/dp/B01IBOBY74/ref=asc_df_B01IBOBY74/?tag=hyprod-20&linkCode=df0&hvadid=312168100217&hvpos=1o1&hvnetw=g&hvrand=12722544881751214962&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9027395&hvtargid=aud-801381245258:pla-406302983505&psc=1

Is my thinking off on any of this, and has anyone used similar product for the repair, or used a technique that you'd recommend?
Thanks for your help!
-Hayden

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This is a typical problem with aging scrambler pipes, and the many used ones out there are usually in the same shape. Some members have been able to salvage their system by cutting out the badly rusted areas and welding in patches, but it's a touchy situation as the metal is thin and can fall apart easily during welding so it takes someone with good welding skills to get it done well
 

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Discussion Starter #3
This is a typical problem with aging scrambler pipes, and the many used ones out there are usually in the same shape. Some members have been able to salvage their system by cutting out the badly rusted areas and welding in patches, but it's a touchy situation as the metal is thin and can fall apart easily during welding so it takes someone with good welding skills to get it done well
Agreed, it looks like a VERY thin wall. I've got every kind of welder but a TIG (next big purchase on the list), so I don't think I'd have a prayer of not blowing through and sticking slag all over the inside. I feel like that could cause more problems than just having the holes. The weld that the PO did looked like they used a stick welder, or maybe a harbor freight wire welder w/o argon (really nasty). Do you see a problem with submerging the entire exhaust assembly in cleaner and then rust bath? I wasn't sure if the scrambler exhaust has any kind of fiberglass in there (if so, I probably wouldn't want to submerge it.
Thanks again!
 

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I'm a complete novice at welding, but I managed to patch my CL175 can without too much difficulty.

I also used JB Weld to plug a couple of pinholes in my 'finished' welds, and that has held up well against the heat so far.

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Using a Mig welder with CO2 shielding gas.

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Outlet 'spout' was rotted through, so I welded on a new one cut from a Triumph Scrambler can that I'd been playing with.
 

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Discussion Starter #7
Wow that turned out great! As a bonus, the heat shield should really help with covering up our patches. What material/gauge stock did you use for the patch? Also, did you polish the patch out, or is that re-electrocoated with chrome?
I'll be breaking out my MIG for sure then. I've had a lot of experience welding, but usually on heavier gauge structural steel.
Thanks Richard!!
 

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I just discovered a similar area of rust on the underside of the top muffler on my 350. The hole is about the size of a half dollar. I tried to use exhaust tape but the pressure blew it right off after about 30 seconds.
 

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I used 1mm mild steel sheet. In my innocence, I thought I'd be able to weld a continuous seam, as I'd done on some practice pieces, but had to settle for a series of tacks, all joined together. I then smoothed out the resultant mess using a flap wheel in my angle grinder.

Before applying heat proof paint, I smeared JB Weld over the worst bits.

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Just wish I'd used black rather than grey exhaust paint.
 

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Discussion Starter #11
I just discovered a similar area of rust on the underside of the top muffler on my 350. The hole is about the size of a half dollar. I tried to use exhaust tape but the pressure blew it right off after about 30 seconds.
Oh wow that's a pretty good size hole. Yeah I don't know if JB weld alone would tackle a patch that big. Do you weld?
 

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I took it into the shop today and they said they couldn't weld it because it would fall apart under the arc. I guess I am gona have to try JB weld.

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I took it into the shop today and they said they couldn't weld it because it would fall apart under the arc. I guess I am gona have to try JB weld.

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I have to wonder if it's only too thin at the edge of the corroded area. I would think you could oversize the patch enough to weld it to an area with thicker stock. At any rate, if you have to JB weld, I would think you would need something to hold the JB Weld in place for a hole that size, or the JB weld will just continue to collapse into the hole. Maybe you could purchase a loose weave fiberglass matt (not chopped or continuous strand).

1. Rough up the area around the hole so the JB weld has better bonding.
2. Thoroughly coat the back side of the fiberglass mat with JB weld (same as if you were doing fiberglass and resin).
3. Apply the mat with the JB Weld coated side down
4. Then begin to thoroughly press additional JB Weld into the matt with a plastic putty knife. It may require a couple additional coats to cover the grid texture caused by the matt, as well as some final sanding once all coats are complete.

*I'm not sure just how hot fiberglass mat can get before breaking down, but once the JB weld cures, it shouldn't matter if the mat breaks down, as the JB weld is what comprises the structural "shell".

Some of the senior members with more experience may be able to tell you if this is a viable solution. I have never used this technique myself, but if I was facing your problem, that's probably what I would try.

Best of luck!
 

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That's a good idea. I read that aluminum can might not be strong enough. People in other threads have said to try sheet stock and JB weld. I'm not sure how a 100% JB weld patch would hold up. Maybe someone can weigh in.
 
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