Exhaust/Muffler Disassembly - 1982 Nighthawk 450cc

tarn

tarn

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Hi All,

Bought my Nighthawk 450cc 2 years ago, and have done work on the carb but that's about it. My mechanical knowledge is above beginner, but not great so I may be using mislabelling some parts.

I have a hole in the bottom my muffler/cross-over pipe (best photo I took of it, you can slightly see it at the bottom of the photo in the green circle.

1776311783814.png

I'm trying to take it off so I can weld a patch on it, however I'm struggling to get the whole exhaust system off. It seems to me the easiest way to take it off is to disconnected the nuts from the exhaust mounts onto the frame (another photo), and the exhaust pipe joint nut (see p.86 in the Honda CB450 FSM).

Is there a better way I should be doing this to take the muffler/cross-over pipe off? It seems it's easiest to unscrew those parts mentioned above and pull the whole system forward out of the header.

Thanks in advance.
T
 
The "crossover" is actually called the Power Chamber. It's an important part so it's good you're working on repairing.(y)
Once the mufflers are off you should be able to remove the chamber and pipes as an assembly.
Remove the muffler mounting brackets and loosen the muffler clamp, actually remove the bolt and spread the clamp. Now the fun. Start working the muffler back and forth to break the seal. Take time and effort. You'll be replacing #14 in this fiche https://www.partzilla.com/catalog/honda/motorcycle/1982/cb450sc-a-nighthawk-450/muffler when reassembling. Some people have used heat(torch) to help.
 
LongDistanceRider said:
The "crossover" is actually called the Power Chamber. It's an important part so it's good you're working on repairing.(y)
Once the mufflers are off you should be able to remove the chamber and pipes as an assembly.
Remove the muffler mounting brackets and loosen the muffler clamp, actually remove the bolt and spread the clamp. Now the fun. Start working the muffler back and forth to break the seal. Take time and effort. You'll be replacing #14 in this fiche https://www.partzilla.com/catalog/honda/motorcycle/1982/cb450sc-a-nighthawk-450/muffler when reassembling. Some people have used heat(torch) to help.
Click to expand...
Gotcha. I'd want to remove 3 parts separately from the bike instead of at once?

Currently I'm pulling 7&14 towards the front of the bike with the power chamber and both muffles attached, hoping to pull it through. But you're suggesting a pull the mufflers (8 & 18) out of the power chamber (be mindful of the bolts and what not).
 
Most people have done the mufflers but I don't see any reason doing the pipes is much different. I remember someone actually pulled the entire assembly out with great difficulty.
 
LongDistanceRider said:
Most people have done the mufflers but I don't see any reason doing the pipes is much different. I remember someone actually pulled the entire assembly out with great difficulty.
Click to expand...
Sorry, can you clarify what you mean here?

Most people have pulled the mufflers off first, then the power chamber off next?
 
tarn said:
Sorry, can you clarify what you mean here?

Most people have pulled the mufflers off first, then the power chamber off next?
Click to expand...
What is meant is the mufflers come off, then the power chamber plus pipes. The entire assembly should be able to be removed except it runs into the tires and center stand, if the bike could be suspended with the wheels removed and center stand up/down it could be maneuvered around for clearance. Being heavy means 2 people to handle it.
 
LongDistanceRider said:
What is meant is the mufflers come off, then the power chamber plus pipes. The entire assembly should be able to be removed except it runs into the tires and center stand, if the bike could be suspended with the wheels removed and center stand up/down it could be maneuvered around for clearance. Being heavy means 2 people to handle it.
Click to expand...
I think I'm following.

I don't necessarily have a way to prop the bike up with wheels removed and maintenance stand up/removed.

But if I pop the mufflers off the back, I should be able to pull the power chamber back towards the rear wheel separating it from the exhaust pipes? Might need to use a heat to break the seal like you mentioned.

I found this thread that seems to have successfully removed the whole assembly like I was trying to the other night. Likely a two person job to be able to pull and wiggle the whole system forward towards the front tire. The trick will be getting it under the bottom of the crankcase.
 
If possible, you might try to leave the power chamber attached to the frame or engine, whichever it is, or whichever it "hangs" bolted from, and then to remove each head pipe individually from the power chamber. And, then, remove the power chamber as the last of the 5 exhaust components to be removed.
Although, It's more likely that the headpipes won't come out like that because they'll need to be wiggled left-right while pulling out...

And as LDR mentioned, I would have a second person to not only hold the bike upright while you wrestle but also to hold upright and rearward if you are pulling headpipes forward.

I haven't yet attempted exhaust removal on either of my 2 450s, but I remember reading how it can be quite a wrestling match !
I've also thought about doing this between 2 stout trees where I tie the bike upright with strong capable ropes on each side to each tree so there's no chance of bike falling onto its side...
 
Last edited:
Thanks all.

Figured I'd give it one last attempt to pull the whole exhaust system off and it ended up coming off. Once I got it off it's spot it actually came out fairly easy. Pull it straight out and down towards the front tire.

https://imgur.com/a/exhaust

Now to decide if I want a new power chamber and/or mufflers...
 
I ended up getting it off, and all welded up and hit with some heat resistant paint.

However, I feel like my pipes aren't going into the header correctly. I cant remember if it sat flush inside or if there was a bit of a gap.

https://imgur.com/a/zJrTQXz
 
It feels like it should go in more straight with the holes, but maybe I'm wrong. I tried twisting it and I can't get them to move. They seem to be rotated the opposite direction the same amount so I'm wondering if it's intentional .

Here's a couple more photos without the cover:
https://imgur.com/a/ivb1tzh
 
It appears the right pipe is shifted right from center, could be picture angle.
Once the collars are on you'll get a better idea of pipe centering. When the collars are tight there'll be @10mm of threads showing.
 
tarn said:
It seems both are a bit off. I've tried gently malleting it over a bit, but it's not wiggling.

Not sure how this even got twisted, but must have when it was getting welded I suppose.

Any tips to twist it? Or just some deep creep and heat?
Click to expand...
Yes to both, the seal needs to break loose some. Gentle malleting won't do anything, heavy handed smacks should help.
 
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