| Author | Message | ||
     Toronto_s3 |
So I am having this recurring problem with the race muffler on my '97 S3. The muffler has been chewing through the aluminum rivets on the front casting of the muffler and then falling apart. Luckily I have that recall cable thingy on the can that keeps it from dropping down and making contact with the pavement. I have the can set up on the rear of the bike so that it swings ever so slightly when hand pressure is applied and obviously the auto clamp joining the collector on to the pipe clamped down securely. This is the third time so far this year I have had this same thing happen to me and I've had to re-rivet the muffler back together. The same thing happens if I use stainless steel or aluminum rivets. I prefer to use the aluminum rivets because the stainless ones are a bitch to drill out if I have one or two remaining after the muffler shakes itself to bits. All of the isolators on the bike are fine and all the mounts are good too. The collector and the inside of the muffler inlet have both lost metal and are now noticeably thinner because they have been rubbing against each other and wearing down. The collector from the header is now about an 1/8" narrower than it used to be. I have had this exhaust on the Buell (in one form or another) for about 9 years now. This is my third race header and second can. I am freaking out that that I may be moving on to my fourth header if I can't figure this thing out. First header broke at the front cylinder exhaust flange. Second header broke at the weld where the two pipes connect. Thankfully this header has been good to me for about 5 years now but damn it scares the hell out of me to lock everything down tight and to have it break some place. Any thoughts? | ||
| Tattoodnscrewd |
I have a race exhaust on my 99 M2 ... the rear mounts are the same as yours and I don't have mine loose in the rear, same with a friends 98 S3T... I don't think you should be able to swing the can at all, it should be secure .. from the sound of it, the allowed movement in the rear mounting is what is causing your problem up front - if it is tightened at the rear mount the front won't have any stress points, it's designed to move with the vibration of the engine - so when the rear mount allows vibration it is going to attack the weakest point - which would explain loose or broken rivets, and the collector rubbing against the inlet to the can. I'd suggest tightening up the rear mounts so it isn't allowed to move independently of the front. | ||
| Toronto_s3 |
Due to the fact I have gone through two exhaust headers my Buell mechanic had told me that the can needs to be able to "swing" just a little bit at the rear hanger. Theory being that if the can is locked down rigidly in place the header essentially bashes itself into the can as the engine moves in its mounts, thus the previous header failures. Unfortunately the same mechanic is now wrenching for a Buell race team so I no longer have him around to set up the system for me. I'm not sure what kind of black magic he performed on the exhaust to keep it intact previously but now its been shaking to bits on me. So what you are telling me is that I should have the can set up rigidly in the back end? The two rubber isolator bushings on your bike that suspend the back end of the muffler, don't they move around a little for you? You have those snugged up tight so they don't move at all? | ||
| Tattoodnscrewd |
Mine is solid, even with the rubber bushings - I think those are there to help reduce vibration to the muffler, not to allow it to swing.. didn't require any extra torquing or anything .. I might have the smallest bit of movement, but not enough to call it movement... I don't really see how the header would bash itself into the can if rigidly mounted as every mounting point of the exhaust is attached to the motor, like I said it's designed to shake/vibrate/move with the motor.. What sounds more feasible is that if the rear is loose, the rear will lash around a bit more than it should .. and from the sounds of it .. cause the problems you have a up front Picture the rear of the can moving while the front is rigid - I can absolutely see the header to can connection getting weakened, that is why your rear rivets are not affected, only the front where the stress is created from a swinging can ... That's my theory at least - if you've been running the rear loose and have been having constant problems - can't hurt to snug up the rear. Good luck and I hope you get it taken care of. | ||
| Davefl |
The Race muffler on my S3 had stainless rivets. I would bet that would be your problem as aluminum does not have nearly as much shear strength at stainless. | ||
| Daves |
I'm thinkin the problem is the flopping of the muffler. Buell + loose exhaust = broken exhaust | ||
| Blake |
You need stainless rivets, good ones, preferably structural grade that leave a solid mandrel inside the hollow. I also agree that loose is bad. Get that muffler clamped down as tightly as possible to the engine. I recommend using the neoprene bushings that American Sport Bike has. Bottom line though for me is that the race exhaust for the tube framers is not street worthy on a long term basis, not if you are going to ride it aggressively anyway. If your collector has lost 1/8th inch in diameter due to clamping and wear, you might consider having a muffler shop expand it back out to proper size for you. You can also have broken headers repaired/welded; no need to throw them away. Trust me, I know. After welding, have the weld needle gunned thoroughly to help relieve residual tensile stresses. And if you really want to help the header in the collector area, have a couple gussets welded on either side of where the two header pipes first come near each other. See following...  | ||
| Blake |
That will hopefully prevent the two head pipes from vibrating excessively to the point of causing a fracture at the collector. It is important to avoid welding the vertical ends of the gussets where the reliefs are cut. Welds there can cause stress peaks that will be susceptible to fatigue cracking, which is what the whole reinforcement scheme is trying to help prevent, albeit at the collector. The further from the collector you can accomplish a reinforcement scheme like shown above, the better it should work. The idea is that the individual header pipes are each acting like a big tunning fork. The reinforcement is intended to shorten the vibrating part of the tuning fork thus increasing the frequency at which each head pipe vibrates, which in turn greatly diminishes the magnitude of vibration and the cyclic fatigue stresses that result from it. The welds on the gussets may eventually fail, but that seems so much better than having a head pipe at the collector come apart. Hopefully the reinforcement will eliminate such failures entirely. Shot peen the welds if you can or have them thoroughly needle gunned, especially at the upstream end where flexure from vibration is initially constrained. | ||
| Blake |
The semi-circular relief cuts in each end of the gussets are important. They are intended to reduce peak stresses in the welds and thus to help prevent weld fracture due to cyclic/vibrational stresses. The reliefs help spread the stress out over more of the weld rather than having it all dump into the very ends of the weld. |
