I finally did the sound testing on my DRZ-E and my Son's WR426. I tested both bikes 3 ways. 1. Pure stock 2. Custom made exhaust cap 3. Exhaust restrictor (cap) removed. All testing was done with a Radio Shack analog meter set to "A" weighting, 20" away at a 45 degree angle. The 1/4 trottle setting is just an estimate but all testing was done at the same setting. Lets talk about the DRZ first. The custom cap consisted of a plate with a piece of 1.5" i.d. thin wall tubing 2" long welded to it. The spark arrestor is stainless steel screen welded to the inside. The air box snorkle was removed and jetting richened up. Stock at idle = 84 db Stock at 1/4 throtle = 96db Custom cap at idle = 85 db Custom cap at 1/4 throtle = 96db Stock cap removed at idle = 93db Stock cap removed at 1/4 = 102db The WR426 gave very interseting results. The custom cap (actually an insert) is a plug with a 3/4 inch hole drilled thru and retained by the stock restrictor screw. Stock jetting and stock air box. Stock at idle = 83 db Stock at 1/4 throtle = 116 db Custom insert at idle = 85 db Custom insert at 1/4 throtle = 110 db Stock restrictor removed = 92 db Stock restrictor removed at 1/4 throtle = 116 I can't understand why the stock insert and no insert gave the same reading. They have a different sound, but the little stock insert is very loud in a different way. I suspect that the frequencies are different to our ears but the meter can't tell the difference? Tests were run several times to make sure of the results. Any way, that's what I did. Any suggestions or comments are greatly appreciated. I will post this at the Yamaha site and on DRN as well.