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Exhaust question. 1978 cb750k

Tristan

CB750 Enthusiast
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I just recently purchased my new to me 78'. It came with a terrible home-made 4-2 exhaust. I bought the MAC 4-1 exhaust to replace it. I thought 8 nuts and 2 bolts for the hangers no problem. The Mac came with pipe joint collars (half moons) but they where not the correct ones. The headers did not make a complete seal once the flanges were bolted down. I thought "no problem" I'll just use the half moons from the old exhaust. Honda Part number 18233-392-000 (stock part) it didn't work. The diameter on stock header (and crap header) are smaller than the MAC header.

Please help. All Exhaust Joint Collars I have found are stock and not for custom exhausts. I see a ton of 78' 750's with this exhaust. How? Any idea?

Thanks
Tristan
 
Umm, those collars are just spacers and don't provide a seal themselves. Sure you put them on in the right direction? When I got a '77 it was all new to me and I put the collars on backwards so of course I had a major exhaust leak. And, yeah the stock spacer collars won't fit on the MAC pipes.
 
Thanks jackbeagle! So the half moons do not slide under flange? I guess I had it backwards. I'm headed home to try again.
 
Thanks!

I got it man. I tried 20 different things yesterday so when I tackled it today it was a cinch to remove old exhaust and install the new one. I did it in 45 min start to finish. I can't thank you enough.

Next up is my clutch!


Umm, those collars are just spacers and don't provide a seal themselves. Sure you put them on in the right direction? When I got a '77 it was all new to me and I put the collars on backwards so of course I had a major exhaust leak. And, yeah the stock spacer collars won't fit on the MAC pipes.
 
No problems - it took me awhile to figure it out the first time too. :)

There's an excellent thread over at the SOHC4 site about getting the alignment correct so you don't break the clutch lifter plate. I highly recommend it when you install your clutch plates.
 
The biggest thing with the lifter plate is to make sure you tighten or loosen the bolts a little at a time. If you tighten one first you will snap an ear off the plate, especially with stronger springs.
 
http://forums.sohc4.net/index.php?topic=106700.0

Not to get too far off topic for the original posting, but what I was referring to is the alignment of the pressure plate as per the attached Link. I never saw this mentioned in any of the repair manuals so I guess it was dumb luck I didn't break more of them.

But you're right of course that you need to be careful about alternating tightening down the bolts, but I was really careful and still broke off the plate ear.

Just a suggestion...
 
I have the old exhaust. I'll send you a pic soon. It is an old 4-2 somewhat chrome exhaust.
 

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New Exhaust on bike.

Here are a couple shots of my work in progress on my daily driver.
 

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