I've been riding mainly trials bikes and quiet 4-strokes (XL250) for the past 30 years and this year got my first MX bike (KX100). Stock, it is so loud at high rpms it gave me a headache. I added a dbSnorkel and wrapped the pipe with silicone and rubber and it has made a huge difference. 1st layer is made from a silicone baking sheet, then another layer, then a layer made from a truck inner tube. Used silicone tape to finish the ends. It made the pipe weigh twice as much. Much of the annoying high pitch was coming from the stock expansion pipe. At low rpms it is whisper quiet. I can now actually hear the piston, crank and gears working.