- Jan 25, 2000
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Taken form the MXA site -
"The 2008 Yamaha YZ450F muffler is six inches shorter, 0.6 pounds lighter and packed with a special heat-resistant glass wool when compared to previous four-stroke mufflers. Unlike a conventional muffler, which has a straight-thru “perf core,” the 2008 YZ450F muffler uses a normal, if slightly over-size, perf core, with two piggyback cones (made from perforated metal) inside the over-size perf core. Although the cones shapes are perforated, the second cone is attached to a section of unperforated tubing that runs over the last one-third of the muffler overall length.
Exhaust enters from the mid-pipe to the over-size perf core, where it is met by the first of the cone shapes. Some of the exhaust gases can bypass the first cone (around the outside diameter), but the majority must flow through the perforated cone, where it encounters the second cone (and repeats the process again). The muffler is packed with long strands of glass wool (there is no pillow). Yamaha will offer rebuild kits of the glass packs for $75. There also is no stainless steel mesh wrapped around the over-size perf core (as on the 2007 muffler).
How loud is it? It is AMA legal, which means that it is under 99 dB. It isn’t not ultra-quiet because Yamaha’s intent was not to build a super stealth muffler, but to save weight and move the weight they couldn’t save forward on the chassis."
Note: The yellow cone won't be painted yellow and there won't be a cutaway - this is only demonstrative.
"The 2008 Yamaha YZ450F muffler is six inches shorter, 0.6 pounds lighter and packed with a special heat-resistant glass wool when compared to previous four-stroke mufflers. Unlike a conventional muffler, which has a straight-thru “perf core,” the 2008 YZ450F muffler uses a normal, if slightly over-size, perf core, with two piggyback cones (made from perforated metal) inside the over-size perf core. Although the cones shapes are perforated, the second cone is attached to a section of unperforated tubing that runs over the last one-third of the muffler overall length.
Exhaust enters from the mid-pipe to the over-size perf core, where it is met by the first of the cone shapes. Some of the exhaust gases can bypass the first cone (around the outside diameter), but the majority must flow through the perforated cone, where it encounters the second cone (and repeats the process again). The muffler is packed with long strands of glass wool (there is no pillow). Yamaha will offer rebuild kits of the glass packs for $75. There also is no stainless steel mesh wrapped around the over-size perf core (as on the 2007 muffler).
How loud is it? It is AMA legal, which means that it is under 99 dB. It isn’t not ultra-quiet because Yamaha’s intent was not to build a super stealth muffler, but to save weight and move the weight they couldn’t save forward on the chassis."
Note: The yellow cone won't be painted yellow and there won't be a cutaway - this is only demonstrative.
