MAC #001-0808 4 into 2 exhaust system on a 1980 Honda CB650C

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Chris
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MAC #001-0808 4 into 2 exhaust system on a 1980 Honda CB650C

Postby Chris » Sun Jul 15, 2007 11:55 pm

Here is a description of my install of a MAC #001-0808 4 into 2 exhaust system on a 1980 Honda CB650C. MAC states that this item is not meant for 650Custom's, but I had to try it for myself. First, here is a picture of my bike with it's butchered 4 into 4 system begging to be replaced:
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If you look closely, you can see that the original mufflers had rotted off. Someone welded makeshift collectors onto the ends of the downtubes and then shoved the rotten mufflers into those. I was ok with that last season, but this year I started thinking about making room for a decent sized set of saddlebags. This was a perfect excuse for me to upgrade my rigged exhaust to a 4 into 2 with turnouts. When I found the set that I wanted though, the description said '79 - 82 CB650(NOT Custom)'. What the hell do they mean, 'NOT Custom'? They don't list any other set for Custom's. What's the friggin' difference? One of the guys at work has a 'regular' CB650 and it looks just like mine, but with different handlebars and spoked wheels. I googled to see if anyone else had tried to use these on a Custom model, but found nothing. I found an eBay store that had the headers I wanted and asked the seller if he knew why why they wouldn't work on my bike. He said that he'd sold these pipes to customers with CB650Customs, but that he'd never heard back whether they fit or not. The seller was nice enough to offer me a modest discount on the pipes if I would be willing to document the installation for him so that he would be able to use it to answer any future inquiries. It sounded like a pretty good deal to me.
When the exhaust arrived, I opened the box right away and inspected the contents. The first thing I noticed was that there were no installation intructions included. I already knew from my pre-purchase research that I could find the instructions here: http://macperformance.com/store/PDF/001-0808.pdf . They're not great, but they do point you generally in the right direction, I guess :? . The next thing I noticed was that inside one of the mufflers, at the rear of the baffle, one of the tack welds that hold it in place was burnt through leaving about a 1/4" hole:
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Great, it seems like almost everything I buy anymore needs to be fixed before I can even use it. :evil: I expected a little more from a brand name like MAC and not made in China. Oh well... par for the course. They were bare metal on the inside too, which means they'll rot from the inside out... a little pre-rusted even. Other than that, the chrome was beautiful.
The next morning, I set out to install my shiney new exhaust. Because I had already decided that any clearence issues would be with the center/sidestands, I measured where they were at with my current exhaust. With an assistant (wife) holding the bike upright, I measured 5 1/2" from the lowest point of the centerstand (foot) to the ground. The pad attached to the stock muffler, where the centerstand rested, measured 8" from the ground. And the sidestand was about 7 1/2" from the ground. Knowing that the left side would be the most difficult because of the stands, I started there. I removed the old exhaust and installed the new, loosely at first, until everything was positioned the way I wanted it and then I tightened it all up. I took pictures of the new left side and the old right side together to show the differences:
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Then I moved on to the right side and got it all bolted up. Upon starting the bike, I noticed exhaust leaks at both the flanges and the muffler clamps. Jeez! I had to be at work in 2 hours and I didn't wanna leave the bike home on such a nice day. I checked my Clymer manual for a diagram to see if there were supposed to be gaskets on the flanges. No luck. The exhaust section in there is very vague. But I found an exploded view on a website that sold parts for metric bikes, and sure enough, there's a copper gasket on the exhaust flanges. So I took the headers back off and used a sharp tool to scrape away some of the carbon to reveal a gasket. Then I pryed it out to have a closer look, destroying it in the process. They're very soft. If I hadn't torn it up so bad taking it out, I might've been able to get away with turning it around and using the side that wasn't imprinted with my old flanges.
So I got in my truck and drove to the nearest bike shop... 'Closed on Wednesday' Who'd ever heard of such a thing? So I drove to the next closest shop a few miles away... 'Closed on Mon., Tues., Wed.' . Am I missing something here (besides my exhaust gaskets)? I hopped back in the truck and drove around for about a half hour looking for an obscure little bike shop that someone had mentioned to me recently. When I finally found it, I was relieved to see some activity at the place along with a whole bunch of nice CB750's and the like outside... lots of vintage metal. This place would have what I needed for sure. When I walked inside, I was interrupting lunch. I felt bad for that, but I was in hurry and showed them the gasket I needed four of. One of the older gentlemen handed a box of gaskets to a younger man and asked him to look through it for me. I found out that motorcycle exhaust gaskets come in all sorts of shapes and sizes, but we finally found a matching set of four and confirmed with the older gentleman that they would work for my application. Back in business for $5! I grabbed one of his cards on my way out the door. These 'nuts and bolts' kind of shops are hard to find around here.
1980 CB650c

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Postby Chris » Mon Jul 16, 2007 12:42 am

I hurried home and dug out the other two gaskets. Yeah, two. It seems only three of the four were in place, but I guess you get stuff like that when you buy a $400 motorcycle that's 30 years old. It's still the best investment I ever made. I installed the new gaskets and that took care of the exhaust leaks up front. The rest would have to wait until I got home from work.
On my ride to work, I noticed that this system was considerably louder than my old 4 into 4 with the rotted out baffles. It kinda sounded like someone had installed H-D mufflers on a SOHC Honda :? A bit of a tinny, hollow sound like a little engine with big pipes. And it had a funky note on the right side muffler that I chalked up to that weld that was burnt through. On a left turn, something scraped the ground and I thought to myself, "Oh great, there goes the shiney new chrome!" And then on a right turn into the parking lot, the same thing happened. But when I checked the tips of the mufflers, I didn't find any marks on them. Later on when I showed one of the guys, we found scrapes on the centerstand. It was much lower than before and the arm was resting against the muffler, keeping it from swinging all the way up where it should've been:
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Work was slow and I went home at lunch time. This doesn't happen often, but I lead a charmed life and I needed to finish my install :lol:
When I got home, I tried tightening the muffler clamps some more to stop the leaks. One of the grade 5 bolts snapped, so I walked to the hardware store for some grade 8 hardware. Nuts, bolts, flat washers and lock washers for a little over $3. This also gave me time to consider that a slip fit should not be so hard to seal. I got back from the hardware store and removed the right side muffler to check for burrs where it was notched (for clamping). Sure enough, the fellas at MAC had run an abrasive in the area just enough to get paid for it, but the burrs were still there:
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This would explain the leaks. So I burred my new mufflers, welded the burn-through on the right side baffle, and as an added measure I applied some high temperature RTV over the abrasions to help seal the joint. I put everything back on the bike, but didn't start it because I wanted to let the RTV cure overnight. Then I turned my attention to the centerstand. It was almost 2 1/2" lower than before and wasn't going to go any higher unless I modified the arm that was contacting the muffler on the left side. So I used a cutoff tool to notch the arm down by the foot and straighten the bend in it:
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Then I drilled a new hole in the 'centerstand stop bracket' that came with the headers in order to get it where I needed it. This brought the stand back up to where it was with the old pipes and it was no longer resting on the new chrome. The side stand was still contacting the muffler, but in a place where I don't think it will do too much damage before I figure out a way to protect the chrome.
I was unable to find any way of quieting the mufflers, but after riding with them for over a month I've grown a bit more accustomed to the new sound. I also had to modify the main stand once more since the original install because that lever was still sticking out a little too far:
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My new saddlebags came last week. They're much smaller than what I originally had in mind, but I like the way they fit. I'll take some fresh pictures soon to show you what it looks like now. I hope this posting was helpful for anyone looking to install these pipes or a similar set on their CB650.
1980 CB650c

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1980cb650
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Postby 1980cb650 » Mon Jul 16, 2007 11:45 am

That's a nice how-to Chris. I hope my pipes last as long as I have the bike. I actually do like the stock look and the stock sound.

Did you have to change your jetting to make these work, and have you noticed any performance differences?
--Andy--
--1980 CB650--

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Postby Chris » Mon Jul 16, 2007 12:47 pm

Thanks, Andy. I liked the stock look as well, but I got it in my mind to replace the rotten pipes and didn't wait for a deal on a decent set of stock 4 into 4's. Other than it being much louder, I haven't noticed any performance changes good or bad. It sure makes alot of noise though :lol: . Personally, I would've preferred quieter mufflers. MAC claims that rejetting is not needed and I was unable to get a reply from the PO whether my carbs have been worked or not.

Here is where the main stand ended up:
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And here are some photos that I took today with the saddlebags installed:
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Last week at the union hall I parked her next to a Sportster and took a long hard look. I love my CB650! :D
1980 CB650c

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Re: MAC #001-0808 4 into 2 exhaust system on a 1980 Honda CB

Postby Volker_P » Tue Jul 17, 2007 3:48 am

Hi Chris,
fine description and great pictures. :D I think it is quite hard to beat the original exhaust with regard to loudness without loosing power. Another advantage is that you can get out the rear wheel without loosening or removal of the exhaust. Disadvantage is that it is quite heavy.
Presently I am considering whether I should spend 500EUR for a new, original 4-4 or just continue welding the silencers for another 15 years ...

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Postby Chris » Tue Jul 17, 2007 11:46 am

Thank you, Volker. Yes, a new stock replacement would've been great, but much more expensive. These pipes are a lot thinner than stock, which probably explains the 'tinny' sound. The silencers have mechanical baffles inside. I emailed MAC's technical department and asked if there were any additional silencers that could be fitted inside the collectors or something, but they couldn't help me. If the chrome finish on the primarys doesn't last, I may install some header wrap on them and that should quiet them down a little more. They're not quite what I expected, but I am getting used to them. I do like the way the look on the bike. As for rear wheel removal, it doesn't look as though that will be an issue and it's actually easier to lube the chain now. Also, I mentioned that the exhaust is bare metal on the inside... one of the guys at work plays with vintage Triumphs and said that he likes to coat the inside of a new set of headers with high-temp grease. It's too late for me to do that as mine are now coated with carbon deposits, but a good thing to keep in mind. This thing screams at WOT and the cops come quickly :lol: I have yet to find a way to get a quality sound recording to share with the forum. Any suggestions?
1980 CB650c

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Postby Volker_P » Wed Jul 18, 2007 1:33 am

Hi Chris,
I spray a bit of oil (1:1 fuel oil /engine oil) into my silencers directly after a longer turn before the condensate can develop. I think 15 years and 70000km are a good reference for that procedure although from time to time some welding is required. The last silencer still without welding starts to show a rusty spot now. :cry:

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Postby Chris » Wed Jul 18, 2007 10:15 am

:) Another excellent idea! Thank you, again, Volker.
1980 CB650c

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Re: MAC #001-0808 4 into 2 exhaust system on a 1980 Honda CB650C

Postby Chris » Sun Jun 01, 2008 12:36 am

Just wanted to give everybody an update on these pipes. The chrome doesn't seem to be holding up very well and I might have to look into some header wrap or ceramic powder coating this Winter.

Don't expect these pipes to last as long as the stockers. They won't even come close. :x
1980 CB650c

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Re: MAC #001-0808 4 into 2 exhaust system on a 1980 Honda CB650C

Postby old gringo » Sat Jul 12, 2008 4:15 am

Nice info Chris. As you said, my bike already had them on when I got it so I don't have a baseline reference as to the sound. I personally like the sound but it might be louder than some would like. I wear a full coverage helmet that is a little quieter inside. I did notice that with a half helmet it was quite a bit noisier however. Don't know for sure if mine are MACs or not.
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Re: MAC #001-0808 4 into 2 exhaust system on a 1980 Honda CB650C

Postby Chris » Sat Jul 12, 2008 8:56 pm

Hi, gringo. There aren't any markings on these to identify them as MAC's, just the box they came in. From the pics I've seen of your bike, my guess is that yours are the MAC's as well. Yes, a full-faced helmet makes a big difference. I wear a modular and sometimes open it while I'm underway for one reason or another. You can really tell the difference then. :lol:

BTW, I bet I know why you don't have a centerstand.
1980 CB650c

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Re: MAC #001-0808 4 into 2 exhaust system on a 1980 Honda CB650C

Postby old gringo » Wed Aug 06, 2008 6:49 pm

BTW, I bet I know why you don't have a centerstand.


Actually I do have the stock center stand. No problems, but mine is a standard model not a custom, not sure if that makes a difference.
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Re: MAC #001-0808 4 into 2 exhaust system on a 1980 Honda CB650C

Postby Chris » Tue Aug 19, 2008 7:10 pm

Interesting. So maybe the center stand is the only reason why MAC says these pipes won't work on the Custom model? I'll have to keep an eye out for a side by side comparison of the stands between the two models. If this is the case and they are different, finding the stand from a standard bike could save somebody a little work in the future.
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Re: MAC #001-0808 4 into 2 exhaust system on a 1980 Honda CB650C

Postby Volker_P » Wed Aug 20, 2008 1:07 am

The stands of Z-model and custom look basically similar but are not identical. Don't remember whether you could use the Z-model center stand on a custom (RC05) at all, but quite certainly not with the 4-4 exhaust without changing anything.
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