Topic: Heads-up for anyone thinking about buying a used MAC exhaust.

[ultragoat]

I thought it time to replace my straight headers (no mufflers) on my 78 CB750K so I bought a used MAC 4into1 exhaust on eBay. I received the exhaust and thought that I could just use my original Honda "split collars" (I think Honda calls them exhaust joint collars). But when I went to mock them up, the split collars were too small  The head pipes look like they're the same size , but the MAC is just a little larger in diameter, so the collars won't fit.

Here's how the collars are supposed to fit:


But here's how the original Honda collars fit on the MAC  :




My first inclination was to grab some vice grips and/or a hammer and make the suckers fit!  But in a rare instance of clear and rational thinking, I decided to consult this forum and found that some others had run into the same thing, but they weren't clear on how they solved their problem.

So I looked on the MAC website for the collars. No luck there. Scoured eBay. No luck. I was about to head to the motorcycle salvage yard in an off chance that they had some. I first decided to email MAC and ask them if they could help. I really didn't think they would even reply but not only did they reply, they said they had the collars for sale and a couple of days later, I received them.

Here's the original collar on the left and the MAC collar on the right:


And here's the MAC collar on the MAC exhaust all ready to bolt up  :


If anyone is thinking of buying a used MAC, you might need some MAC collars (maybe some MAC's are the same diameter as the Honda pipes so you can use the Honda collars?) so make sure you get them with the exhuast or you'll have to get them from MAC. They aren't listed on their website so you'll have to email or call them. They're really helpful when you get them on the phone.

[Hasenkopf]

btw I used the mac collars that came with the mac ex system.......saved my old ones, but did have to modify the mac parts a bit, like deburring and stuff..... the pipe is cheap for a reason, and few things like these are ever perfect.....just my .0000002

[famoussas1]

so the collars come with the exhaust when you buy it new? 

just curious cuz I'm thinking about buying a mac for my cb550k and wanna plan ahead for parts and what not.  hope i dont have to rejet my carbs.

[CB750Ken8]

I've used the old honda ones that are "too small" turn them around the other way so the collar pushes on the flare, the straight part pushes the exhaust onto the head, the only part that might be bad is the exhaust might leak, not sure though, dought it since Its the way I use them and the bike ran fine till the hole electrical and fuel issues thing.

[Quorthon]

so the collars come with the exhaust when you buy it new? 

just curious cuz I'm thinking about buying a mac for my cb550k and wanna plan ahead for parts and what not.  hope i dont have to rejet my carbs.

Just did a new 4-1 mac on my 72 cb500.  They did not come with collars.  My stock ones worked fine.   You do have to get doughnut gaskets though.

[famoussas1]

where can i get those gaskets?  got a part no. handy?
is this the gasket you speak of? (off Z1 enterprises) Exhaust Gasket Honda CB550 XL600 VF750 GL1500
KL16-5976-1
OEM: 18291-MN5-650---
Exhaust Gasket - 32mm x 40mm x 4.2mm
Fits Honda CB125S/S1/S2 CL125S/S1 CB250 CM250C CMX250C/C2/CD CB500/K1/K2 GB500 VF500C/F XL500S/R CB550/F/K1/K
$1.90


did you have to rejet your carbs as well?

thanks.

[Quorthon]

Those sound right.

I haven't rejetted after my pods or exhaust.  It seems to run fine like this but I never rode it really before doing these two things.

From what other people say it probably needs some carb tuning but it works fine like this for now.