Unfortunately, I found this exhaust to be too loud. I've never cared for loud mufflers for the sake of loud mufflers and, more and more, loud pipes are falling out of favor even in the motorcycle community. Of course I fully understand that there may be some performance benefits when mufflers and fueling systems are carefully (and professionally) configured. Personally, I'm not riding in situations where performance enhancements are necessary. In fact, putting my money in good suspension components is way-way-way more valuable to me than mufflers and other exhaust components.
Having said that though, I don't know the Supertrapp set up and, for all I know, it might be adjustable and tuned. What I found in my research is that this model Supertrapp can, in fact, be dialed in for a lower decibel level. Essentially, the exhaust is ejected through a series of disks in the back of the muffler, which is why you don't see a hole in the end the muffler in the photo right above.
The first thing was getting the core out.
Core Removal:
Following the Supertrapp E.A.R. instructions, I found it strange that the core is secured in the can with a screw or some other method. There's really nothing holding it in there...which may be why it was so dang hard to get out.
The instructions said to use a 15" wooden dowel and pound the core out from the rear. I started with a rubber mallet and was quickly swinging my small sledge. I had to hit it so many time I totally lost count. I also used penetrating oil. I was worried that there was something holding it in there, but there wasn't and eventually it started to creep out.
While I should be surprised that there was hardly any parking in the can, it's actually not that unusual. The packing breaks down into fibers that work their way out. Actually, if they didn't come apart and work their way out, we wouldn't need to repack these things!
Anyway, I got the core out and cleaned it up with some a a sanding block and some steel wool.
Selecting No. of Disks:
According to the Supertrapp E.A.R. instructions, fewer discs reduce sound level and increase back pressure; more discs increase sound levels and reduce back pressure. More back pressure means better low end torque and worse top end performance. Less back pressure means worse low end torque and better high end performance.
The instructions applicable to the KLR600 provide that 5-6 disks is optimal for the stock engines and stock jetting and 8-10 disks is the "practical" maximum for modified models.
The muffler in my KLR600 had 8 disks...or maybe 9. I clearly had 8 disks, but there was another disk that the instructions refer to as the Reverse Flow Baffle. The difference is the Baffle has a cover and it's unclear whether that should be included in the number of disks in operation. I intend to follow up with the manufacturer on this point....
...but for now it appears that I can at least remove 3 disks that, as the instructions indicate, might lower the decibels.
Repacking:
Before I removed the Supertrapp assembly, I also purchased some 4-stroke muffler packing to repack the muffler. Muffler repacking is another maintenance item that should decrease decibel levels and I've heard it said that fresh packing improves performance.
Generally, repacking is a simple process of wrapping the core in a fiberglass, steel wool or ceramic sound deadening material. The Supertrapp E.A.R. core is 11 1/2 inches long and has an outer diameter of 1 3/4 inches. The core subject to wrap is 9 3/4 inches. The can, although tapered, has a inner diameter of 3 3/4 inches at the back.
I purchased a package of 4-Stroke Ceramic Packing that came in a mat of 12" x 24" x 1" for $18 on Amazon. Wrapping the Supertrapp E.A.R. core required 9 3/4" x 18" of the 1" thick mat. In this case I was able to make two full wraps on the core.
Here's a photo of the wrapped core. Once wrapped the material is held in place with masking tape that, of course, burns away quickly.
The wrapped core must be very carefully slid into the can keeping the wrap in place.
Results:
As usual, I get only half of what I ever want and that's the case here, as well. While there was a reduction in the sound level, it was only about half of what I really wanted. As it is, it's close to that line where I keep or replace it.
Rather than jump to premature conclusions, the plan is to put some miles on and see if changes in the decibel levels arise as the packing material heats up and moves around into possible weak spots.
Stay tuned....
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