Aftermarket Exhaust Mounting Question

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charlieaintthatbright

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I've got a 1981 DOHC CB750K that I bought from a guy who stopped mid cafe racer conversion. I have sorted out most of the miscellaneous things, fixed the wiring, and gotten it running, but I am stumped on the mounting of the exhaust. The 4-into-1 exhaust came with the bike, but I have no idea what brand it is. It came with homemade pipe joint collars, similar to the OEM exhaust pipe joint (PN#18233-425-000) which do not seem correct. Hard to describe, but see pictures. When mounted as shown in the OEM parts diagram the end of my headers are a few mill off and do not seal, even with the copper crush washer.

Anybody know if I need different mounting hardware or if I can shorten the ones I have so that it will seal.

Disclaimer: I'm a moron and don't think I explained this right but any advice will help. Might be as simple as biting the bullet and buying the OEM exhaust collars, but want to make sure I'm not missing anything obvious before I do.

https://imgur.com/a/ctyff0Z
 
I'm not seeing your picture. Are you using new gaskets (copper sealing rings) ? A common mistake is leaving the old gaskets in there, they are hard to see and need to be literally dug out of there with screw drivers and other implements of destruction. Chances are that if you have an aftermarket exhaust the OEM collars are way different and won't work. There are no torque specs for the nuts, just somewhere between loose and too tight. There will be a sizable gap between the collars and the engine, just the way they are.
 
Thanks for the replies. The images are on an imugur, hopefully this link will help.
https://imgur.com/a/ctyff0Z

My guess is that the aftermarket exhaust has its own collars, but I have no idea how to go about finding what collars should work.
Also, its not the torque spec that is the issue, the collar + joint combination just spaced out the exhaust header from the head even when the collar was tightened. Also I used new copper crush gaskets twice on the two styles of collar I used.
 
charlieaintthatbright said:
Thanks for the replies. The images are on an imugur, hopefully this link will help.
https://imgur.com/a/ctyff0Z

My guess is that the aftermarket exhaust has its own collars, but I have no idea how to go about finding what collars should work.
Also, its not the torque spec that is the issue, the collar + joint combination just spaced out the exhaust header from the head even when the collar was tightened. Also I used new copper crush gaskets twice on the two styles of collar I used.
Click to expand...
I was just browsing through some older threads, saw yours, and wondering if you solved this. Your header looks the same as mine which is a MAC. I recall when I got it, they gave me the same exact same collars as you have in your pics. They were useless. I finally took it to a local shop and they installed for me using the stock collars, or ones that looked similar anyways. You have to place them into the exhaust pipe flanges (the things with the fins) so that the thick ends push against the flange at the end of the pipe. The skinny end of the collars face the other way and face towards the front of the bike when installed.
collar.jpeg
 
My aftermarket exhaust im sure was fitted to the bike in the USA before it came here. The collars are very similar to the oem but not quite although do work. Hopefully you discover the issue
 

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