Topic: 77-78 Exhaust outlet diameter

[Hon3ybadger]

Hello everyone! So i used to have the muffler (maybe a mac?) in the attached photo. It has since found it's way to the trash bin. When I built the bike last year someone on here stated my pipes were the stockers for a 77-78 4 into 1 F-er. I want to order a new muffler but, I forgot the diameter of the outside of the outlet for the slip on. I believe it's 2.5 inch but I'm not sure. Anyone know?

[Powderman]

Can't you measure your pipe? What am I missing here?

[hsas.69]

Mac makes a replacement muffler for the stock header.

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[Ericcb750]

Hey honey badger, I also have an F3 header on my CB750k (1978) and just picked up a new F3 for a project. The outer diameter on the stock exhaust 4-1 header is 2 1/8", I'll try and check with my mic what that is in CM. Its not easy to find a lot of exhausts in that size as they're usually 2" or 2 1/4" (like my cone engineering muffler). I had to get some short pieces of exhaust pipe from auto zone and put a spacer in. Also David silver spares sells the original exhaust gasket for the end of the header where the muffler attaches (make sure to get the right one) which has some thickness to it as well....Good luck. let me know if you have any questions. Thanks

[CB750R]

I used a Walker exhaust adapter that fit my header to my mid pipe. Almost every car parts store will have them in stock in many sizes. Part numbers are 41xxx.