Repacking cb 450 mufflers
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Thread: Repacking cb 450 mufflers

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    Member marovn's Avatar
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    Repacking cb 450 mufflers

    I'm trying to figure out the best approach to open up and repack my 73 cb 450 mufflers, wondering if someone has any experience with this.

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    Senior Member ancientdad's Avatar
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    OEM mufflers? Unless someone before you has already done that, they aren't packed with anything from the factory, solid interior baffles as far as I know

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    Member marovn's Avatar
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    Quote Originally Posted by ancientdad View Post
    OEM mufflers? Unless someone before you has already done that, they aren't packed with anything from the factory, solid interior baffles as far as I know
    I'm looking at the cb 450 factory service manual (page 86) and it does show packing behind the baffle.

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    Senior Member bilbikek411's Avatar
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    I have some late model CB450 mufflers (HM319) and they have sealed baffles at the end of the mufflers;I imagine you could cut the end-cap of them off to see if repacking them was possible,but then the end-cap/baffles would need to get welded back on.

  6. #5
    Senior Member 76TWIN's Avatar
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    I see it too in the FSM

    Repacking cb 450 mufflers-untitled.pngRepacking cb 450 mufflers-untitled2.png
    Last edited by 76TWIN; 05-19-2017 at 10:37 PM.
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    Senior Member JamesPal's Avatar
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    The image shown on the FSM page 86 is a Bomber exhaust. The CB450 FSM started as the Bomber manual. As the bike evolved changes were shown in section 7. This post shows the inside of a CL450 muffler: Exhaust muffler cutaway diagram / cross section drawing- or photo - '72 or later ?. This is very typical of the 70s Hm mufflers. Somewhere on the forum is a picture of a CB450 K2+ muffler cut open.

    The '73 CB450 K6 muffler has three chambers. If you look on the inside (near wheel) you can see the spot welds where the chamber plates are. Inside the muffler the exhaust is dumped into the first chamber, there is a pipe that runs from the front chamber to the rear chamber, the rear chamber plate is perferated so the gasses can flow forward to the middle chamber and there is a pipe that runs from the center chamber to the exhaust port.
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    Senior Member ashimotok0's Avatar
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    I have got a couple of nice ...ish Bomber silencers which would need rechroming and a couple of dents knocked out of them. I was thinking of grinding the seams away, separating the two haves and then bead blasting internals, chrome stripping, rebuild the internals and coating with a high temperature coating, reweld and then rechrome. A colossal amount of work I know but my experience of giving what look like nice silencers to just get rechromed just results in heartache due to rotted out internals etc and originals are rocking horse poo NOS. I was hoping David Silvers replicas were going to be my saviour but a Bomber aficionado advised me that the shape isn't correct etc and you can tell a mile off that they are replicas. Why can't repro makers just faithfully reproduce the originals? it's the same with his CB250/350K replicas ..... the seams are too big and look wrong, so I went to the manufacturers he used in Birmingham UK and they made me some with the correct seams, perfectly seam TIG welded and no 'Made in England' stampings. Problem is with the Bomber and CB72/77 silencers that DS sells, he owns the tooling I think so , understandably, the factory can't make individual modifications for customers.

  9. #8
    Senior Member -alan-'s Avatar
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    Quote Originally Posted by marovn View Post
    I'm trying to figure out the best approach to open up and repack my 73 cb 450 mufflers, wondering if someone has any experience with this.
    I went down a similar route wondering if I could reclaim a noisy left-side silencer on my own bike. As the guys say, the later 450s have internal metal baffles which diffuse the gas through a series of chambers to slow the flow, create some back pressure, and reduce the noise. If these are intact, the pipes are fairly quiet at low revs. If they're not, then one/both pipes will be louder and you probably wont be getting the right back pressure. If they are damaged, probably better to repair them - or better, replace them - than repack, which is at best a short term solution, and a bit of an unknown on the flow/back pressure side.

    There is a thread in here somewhere I think showing a silencer which had been dremelled open, and then repaired.

    In the end, I just bit the bullet and went for a decent s/h replacement.

    I think the balance between looks and sound is better than any of the aftermarket ones I've yet come across - but that's purely imo of course
    Last edited by -alan-; 05-20-2017 at 03:52 AM.
    CB450 K5

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    Member marovn's Avatar
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    My mufflers are the HM319s also, if anybody runs across the picture of the cut open pipe could you please let me know where to find it.
    Thanks to all

  11. #10
    Member marovn's Avatar
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    Also, I was wondering what happens to the insides of the muffler in the re-chroming process, does it get chromed too or is it a line of sight type thing?

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