Rust holes in CB200t Scrambler Exhaust
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Thread: Rust holes in CB200t Scrambler Exhaust

  1. #1
    Member TheFreeRenegade's Avatar
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    Rust holes in CB200t Scrambler Exhaust

    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&hvne tw=g&hvrand=12722544881751214962&hvpone=&hvptwo=&h vqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9027395 &hvtargid=aud-801381245258la-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

    Rust holes in CB200t Scrambler Exhaust-exhaust_1.jpg
    Rust holes in CB200t Scrambler Exhaust-exhaust_2.jpg
    Rust holes in CB200t Scrambler Exhaust-exhaust_3.jpg

  2. #2
    Senior Member ancientdad's Avatar
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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
    Tom

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  3. #3
    Member TheFreeRenegade's Avatar
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    Quote Originally Posted by ancientdad View Post
    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!
    75' Honda CB200t



    Vintage or Bust

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  5. #4
    Senior Member ancientdad's Avatar
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    No packing inside Honda's exhaust systems on these old machines. De-rust at will
    Tom

    Ride along at the drag strip - https://www.youtube.com/watch?v=20jFPazXlvU



    running points... because I'm too old for mysteries that begin with pushing

  6. #5
    Member TheFreeRenegade's Avatar
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    Quote Originally Posted by ancientdad View Post
    No packing inside Honda's exhaust systems on these old machines. De-rust at will
    Thanks!!
    Rust holes in CB200t Scrambler Exhaust-yes-meme.jpg
    ancientdad and Bill H like this.
    75' Honda CB200t



    Vintage or Bust

  7. #6
    Senior Member Richard_Pitman's Avatar
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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.

    Rust holes in CB200t Scrambler Exhaust-20190128_152509.jpg Rust holes in CB200t Scrambler Exhaust-20190128_152826.jpg Rust holes in CB200t Scrambler Exhaust-20190202_205917.jpg

    Using a Mig welder with CO2 shielding gas.

    Rust holes in CB200t Scrambler Exhaust-20190128_152548.jpg Rust holes in CB200t Scrambler Exhaust-20190128_152634.jpg Rust holes in CB200t Scrambler Exhaust-20190202_205932.jpg

    Outlet 'spout' was rotted through, so I welded on a new one cut from a Triumph Scrambler can that I'd been playing with.
    TheFreeRenegade likes this.
    1970 Honda CB175K4
    1972 Honda CL175K7
    1999 Honda CB600 Hornet
    1970 - 1972 Random heap of CB/CL/SL 175 parts, slowly being reassembled ..

  8. #7
    Member TheFreeRenegade's Avatar
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    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!!
    75' Honda CB200t



    Vintage or Bust

  9. #8
    Senior Member jakec's Avatar
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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.
    1975 CB400 F0 Stock
    1974 CB550 K0 Chopper
    1970 CL350 K2 Stock

  10. #9
    Senior Member Richard_Pitman's Avatar
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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.

    Rust holes in CB200t Scrambler Exhaust-20190220_144623.jpg

    Just wish I'd used black rather than grey exhaust paint.
    TheFreeRenegade likes this.
    1970 Honda CB175K4
    1972 Honda CL175K7
    1999 Honda CB600 Hornet
    1970 - 1972 Random heap of CB/CL/SL 175 parts, slowly being reassembled ..

  11. #10
    Member TheFreeRenegade's Avatar
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    Wow the final product looks SO good though! It looks like that 175 has had some time put into it, very nice bike!
    75' Honda CB200t



    Vintage or Bust

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