Topic: MAC 4-1 cannister for K5 (Help!!)

[2000daytona]

Just installed the 4-1 MAC on my K-5. I had to pull the original "spigot" fittings from the head as the MAC exhaust system came only with the head attachment on the exhaust where you use the allen head screws. Would someone confirm that this is the only way they are manufactured. It would be a better fit if the finned clamp with spigot system was used. My concern is that after fitting it carefully and slowly with the head tubes sitting on the original copper gaskets at the exhaust ports, I smell exhaust fumes at the header and know that it is leaking where it is attached. What is the general cure for this??? should I get new copper gaskets? did they ship the wrong 4-1? The book says 69-76 K (part number 801-1401). I just spent 2 clams and have no idea how to fix this problem of leaks. I think it is a poor design. Would someone that bought this MAC 4-1 please advise. Any help would be appreciated. Thank 2000daytona.

[Einyodeler]

It`s best to replace the copper gaskets every time you remove and install the exhaust due to the fact that you`ll never get them on in the same exact position that they were.Especially if you switched exhaust sytems as there are usually differences in the mounting angles.
You can get them from Old Bike Barn:

http://www.oldbikebarn.com/part.php?id=3254&subcategory=Exhaust%20Gaskets&bike=CB750&DisplayPerPage=20

[el kabong]

not sure, but this might help:

http://www.kzrider.com/forum/viewthread.php?tid=28305

[sradja]

Are you sure you ordered the right exhaust fot the year of your bike. I have a 1975 cb with a 4-2 MAC Megaphone and it uses the original Flanges to connect.

[2000daytona]

I think I am 99% sure. The 4-1 have the flanges attached already. Well that is what they sent me and the box said 69-76 so who knows. Would some people please clarify. I am about to try some exhaust gasket sealant or try the auto parts store to see if I can make a ring gasket out of some muffler gasket material so when I tighten down the system everything is sealed. Thanks for all the input!!! You meet the nicest people on a Honda.

[Tom H]

I recently put a Mac 4 into 1 on my K6. at first I did not install new copper gaskets and I had some exhaust leaks. So I posted on this site  and someone recomended new gaskets and that did the trick. also try to tighten the bolts evenly when installing and then after you get the engine hot re tighten the bolts again. I hope this helps.

[sandcastcb750]

Sometimes you can get a muffler system to seal using old copper rings, but not always. New rings are a good idea.

I bought a new MAC and a new Kerker; both required removing the old finned clamps and head attachments. Hence the reason new copper rings are needed.

In 1980, I put a kerker on my CB750 K5 that used the finned clamp method, so I could keep the finned clamps. I suspect that in 1975-85 there was enough CB750 business to offer both versions.

The new Kerkers are Supertraps. About twice as expensive as MACs. But they look really cool. Remove the glass wool inside and the sound cool too.