MAC 4-1 Header Collector Diameter

[Guest]

Hey everyone, new member here. Just bought my first Suzuki, a 1979 GS550.
Bike already has a brat style to it so I'm just gonna finish it that way. Picture is in my avatar and signature. All the stock parts are long gone unfortunately.

So my question is could someone with the MAC 4-1 header measure the outside diameter of the collector end? I'm looking at buying it but swapping out the muffler with a Supertrapp and want to know what diameter Supertrapp to buy with it. I've emailed MAC, I've emailed, asked the question on the product page and called and left a message with the retailer (Niche Cycle Supply) but no one is getting back to me so I figured I'd ask on here.

Thanks and I look forward to seeing what this old girl can do! She hasn't run in years ever since the PO chopped her up and couldn't put her back together again.

[GSCafe]

I know this isn't exactly what you are asking but have you thought of stopping by a muffler shop? They can certainly let you know what can fit and whether you need a reducer or expander adapter. They might be able to custom set-up what you want for not too much dough.

[starhawk]

Hoping to avoid all that by just buying the correct ID Supertrapp in the first place! They come in 1/4" steps starting at 1.75" ID. I imagine the collector is probably around 2.5" OD.

[Max]

Welcome to what will surely be an invaluable resource for your winter project. I've got a '79 GS550 as well, very fun little bike and extremely simple to work on, shouldn't have a problem bringing it back to life. I just purchased the Mac 4-1 system and will be installing it this winter and you are correct, the collector OD is 2.5". Many of the Mac products aren't listed on their website, but are still available to order if you e-mail them & request a part no. for order. I know you can purchase only the header for the '79 GS550 for $299, and their newer reverse cone megaphone muffler version of the full exhaust which is not listed on their website. I found the full system on Amazon for $299 new and figured I wouldn't feel as bad tossing the Mac muffler if it lives up to its reputation of being a pile of crap because I still paid what I would've paid them for just the header. Good luck with the bike.

[starhawk]

Thank you so much Max for the info! I've just ordered the black MAC 4-1 along with a 2.5" ID black supertrapp and some new gaskets. I also ordered the full MAC system because it was $305 USD at NCS and I figure I can probably use the muffler on one of my other projects at some point.

I've already cleaned and rejetted the carbs, installed all new orings, so they are ready to go back together now.
Compression is good. Wiring is a mess so that is next up!

Thanks again.