Cutting a muffler down to size?

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Apr 22, 2001
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#1
The muffler on the CRF450R looks like a giant behemoth. But, what would change, if it was cut down to size, enough where it only sticks out pass the side plate by a few inches? Changes performance, noise and/or jetting??

The Glen Helen shot of the bike http://www.fourstrokesonly.com/CRF450RHondaP11.html, not sure if the muffler is similar to, or is stock, just shorter, MUCH shorter.
 

CRGuy

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#2
On a 2 stroke the shorter the silencer the louder the bike and more bottom. On a Thumper the same would apply. Why would you cut the exuast anyway?
 
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#3
Originally posted by CRGuy
On a 2 stroke the shorter the silencer the louder the bike and more bottom. On a Thumper the same would apply.

The interactions between the silencer and the pipe tuning are vastly different between a two-stoke and a four-stroke. The influence of the silencer on wave tuning is far greater on a two-stroke, but it isn't accurate to say that a shorter silencer ALWAYS produces more bottom end on a two-stroke, and the specific length of the silencer on a four-stroke has little or no bearing on power or sound output.

Generically speaking, four-stroke silencers with GREATER volume will TEND to have a lower DB rating, but that ignores a whole host of other factors, so even that statement is fairly stupid to make.

You can count on that fact that a HUGE amount of engineering dollars went into the design of the silencer on the CR450, and random attempts to "improve" at home are only likely to increase the noise and decrease the horsepower. I realize that won't stop people from trying though.
 
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#5
Originally posted by DPW
Here's another good picture of the shorter silencer
Look wise, it looks the same as the stocker, just shorter. Wonder if there is any trade secret difference in the guts.