Mac 4-2, fitmet off and missing nuts. How to prevent leak?

[nezzer]

I just received my mac 4 into 2 exhaust from old bike barn. I am just happy to find a brand new exhaust for my bike since my old one had rusted in half (forum post).

This was supposed to be a exhaust kit for this bike including all mounting hardware. (click for full size)


Pardon me while I vent a little before getting to my question.

The exhaust came with no instructions whatsoever. To make matters worse, it came with 5 bolts and no nuts. I thought that was very strange but I hoped it would be obvious why there were no nuts once I started installing it. (click for full size)


Well, I cant figure out how to mount this thing without any nuts. If nothing else, there is are two exhaust clamp that joins the headers to the muffler that would require a nut and bolt to tighten. Anyways, I got nuts to match the supplied bolts and started installing. It quickly became obvious that the mounting plate to join the muffler to the rear of the bike frame is not long enough. You really have to force the muffler up into place to get the bolt through the mounting plate.

So question #1, has anyone else with an '80 special have this issue with the supplied mac 4-2 mounting plate? If so, did you just fabricate your own?

I kept at it and finagled the exhaust onto the hanger. I then started torquing everything down. I tightened the exhaust nuts onto the studs of the engine to 14 ft lbs. This worked fine on right two cylinders. On the left two the exhaust flanges on the mac system bent long before I hit 14 ft lbs on my torque wrench.

Question #2, anyone else have issues with the exhaust flange being too weak to torque the nuts up to 14 ft lbs?

Thats was a bummer, but I still wanted to hear the thing running so I fired up the bike anyways. I noticed lots of air leaking out of each of the junctions where the headers and the mufflers join up, right where those clamps are. I would prefer to keep the clamps rather than have the system welded. I think getting longer exhaust hangers would help mate up the header and mufflers to reduce some of this leak.

Question #3, have others had to tweak the bend at the headers in order to get everything to line up correctly? Is there any sort of liquid gasket type stuff I can put on this joint or is that regarded as a band-aid fix?

Despite my grumblings, the exhaust system does look great. I hope I can get all this stuff worked out. From the 20 seconds I listened to the system, it does seem quite a bit louder. Not enough to wake your neighbors but much louder than I wanted.

[bikerphil]

Permatex high temp copper for the 2 pipe junctions works well. Slather some on the end of the header pipe and slip on the tail pipe and clamp.

[XSokieSPECIAL]

I used the stock muffler brackets and fabricated a strap to reach the stock mounting holes. ( sorry about the cell phone pics)



I can't really tell from the pics but it looks like you got the system with the turnout mufflers. The are louder than most like, I like them and have a set on my bike with the mack system.

If you want quieter I have a set of bullet tip mufflers for the same system that are a lot quieter and we might work out a trade because one of my turnouts is damaged.



These are in real good shape except the one on the right in the pic has a spot on it were the kickstand was hitting it. (about 4" up from the bottom)

As far as the leaks go, they're gonna leak a little where the splits are for the clamps. You can seal them up wiyh muffler mud or silicone, but it's really nothing to worry about.

Yes, the mounting flanges WILL bend, nature of the beast. Use different nuts to mount them up and they wont leak or come loose. I use these chrome acorn nuts.



Since it's not a stock system you'll have to tighten the nuts a bit more than the manual says but be careful not to damage the studs.

[Ivan]

All the aftermarket exhausts I have seen just used the stock barrel nuts.

[DGXSER]

Even the stock exhaust system can be a PITA to get everything to bolt up. You really need to leave it all loose until you get the mounting bolts in.

Also, did you make sure it was for a Special versus a Standard when you bought it? IT does make a difference.

[XSokieSPECIAL]

Crap!........

What happend to my pics?

They were there this morning!





Never mind..............must be my stupid computer again........there now......sorry

[nezzer]

Those are some brilliant ideas. I had not thought of using the old brackets with the new exhaust. I will also give that copper sealant a shot. I did get the tapper tip mufflers rather than the turn out ones. I have not driven the bike anywhere yet so I can't say yet whether its too loud for me or not. I will post back once I have everything fitted and it stops raining. Thanks for the help.

[nezzer]

As it turns out my factory exhaust hangers were welded in place so I was not able to use them for installation of the new exhaust:


The exhaust hangers on my 1981 xs650 special on the other hand did have detachable hangers. Not only that, but I actually had a spare set from a grab bag of parts I got off ebay years ago to get some highway pegs. Here is the exhaust on the 650:


and the mounting brackets:


After a little work the new exhaust was fitted in place with plenty of copper silicon gasket on the joint to prevent leaks


I have about 30 miles on the new exhaust so far. My first impressions are that it is still louder than I would like. From idle to 3k rpm it has an annoyingly loud hollow rumble. Above 3k rpm it is actually pretty quite, very comparable to the factory exhaust. The bike certainly feels much quicker. It is like it was 8 years ago when I bought it. My rusted out OEM exhuast must have been hurting the powerband. The bike seems stronger in all rpm ranges, particularly up high. This is a pleasant surprise as it was not my motivation for getting the new exhaust. Strangely enough, the left hand exhaust seems louder than the right side. They seem to be putting out about the same exhaust pressure but the left hand side has a more annoying exhaust note. Maybe the lengthy header pipe is resonating in the left hand side muffler while the right hand side is better aligned and not resonating. Some rainy day I will play around more with that and see if I can get the left side to be a little quieter.

[nezzer]

I forgot to mention, I took before and after videos with sound in case someone else is curious about the sound difference. If you are willing to download some pretty big MOV files you might find these interesting.

Factory exhaust on 80 special prior to removal

Mac 4-2 exhaust after installation and all warmed up

[XSokieSPECIAL]

. Strangely enough, the left hand exhaust seems louder than the right side.

Mine seems to be the same way, however I'm not absolutely certain it's not just an "audio illusion".

We all have a dominant eye, why not a dominant ear?

[fredintoon]

There's a test for that.

Mine seems to be the same way, however I'm not absolutely certain it's not just an "audio illusion".
We all have a dominant eye, why not a dominant ear?

Hi Greg
stand behind the bike with it running and check which side sounds the loudest.
Now turn your back and listen again.
If it's still the same side, one muffler is louder than t'other.
If it changes sides, it's your dominant ear.