[quote="high_side"]Reviving an old thread....
I put a set of these pipes on my SuperDuke tonight and holy hell are they loud. I threw in the quiet cores in and at idle there seems to not be a lot of difference. After having aftermarket pipes on my last several bikes, these are by far the loudest. If anyone has any idea how to quiet them down I would love to hear it (if I can over my bike!).]
Same deal. Ordered them with my SD I picked up last month, and thought I made huge mistake. HOWEVER, on advice of Brett at Eric's in Pasadena, got some 17 ga. stainless sheet with 5/32" holes all over it, cut to size and shape and brazed it onto the outside of the large end of the silencer cones, and inserted in the usual place just ahead of the mufflers with small end of cone into muffler. It's perfect. Wife says as I drove away, sound was much less, and lower in pitch. When riding use ear plugs, and can just hear exhaust burble over wind noise at about 60 mph; faster you go, more that wind noise starts to takes over. Still has great torque and throttle response, and seems no/insignificant power loss. The 2:1 conversions on KTM ADV bikes are known to increase torque and about break even on top end horsepower with added backpressure.
Found a piece of this ideal perforated stainless sheet at Paykel, retailers of BBQ and fireplace stuff. It's about 8"x10" and pricey at $15, but you only need about half of it. Also, all edges of cone where you braze on this screen must be cleaned up with grinder/file, so that will fit cleanly into its place in the head pipe attached to the mufflers. Also observed that this connection of 'screen' to cone is virtually unstressed. If you prefer, doing silver solder will probably hold well enough, and can be done with propane torch if you don't have gas welding setup. Problem solved.