Where is the restriction on 05 WRF Muffler

2 replies to this topic
  • jdd123

Posted February 28, 2005 - 12:34 PM


Where's the restriction? I have been comparing the stock muffler (insert removed) with the FMF power core 4 with "quiet insert". Don't laugh :) but when I blew through the stock insert, muffler off the bike, I actually felt some resistance. My friend laughed that there is no way I would feel anyting but to our surprise there was resistance but no black lips. :)

I want a quiet bike for trails. The 450 has plenty of power no matter which pipe I use, but I was thinking the FMF let the engine run better. However, that quiet insert is anything but quiet. Their muffler is light with only a square tube inside. I think it was psychological that I preferred the FMF because I could not hear all the chinsy engine sounds you hear with the stock. But with resistance just blowing into the stock muffler means that there is significant resistance on the low end too? I like to ride below 1/2 throttle and mostly end up >1/4 when fooling around so low end power is paramount for me.

I am worse than an old lady deciding where to put furniture on this one. :p Can't decide which muffler is better. Will the new stock replacement insert from Promotobillet be significantly better in spite of the muffler's internal resistance? Any other thoughts?

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  • Indy_WR450

Posted February 28, 2005 - 12:56 PM


The power core 4 with the quiet core insert sounds great! :)
Throaty but not too loud. Probably around 97 db but deeper sounding than stock. If you want 94 db just stay with the FMF Q series. You can modify the power core opening to quiet her down but you lost the low end that you get from her throat being cleared. :)

  • jdd123

Posted February 28, 2005 - 04:00 PM


Thanks, Ok, I am leaning toward keeping the power core 4 on it because there is absoluty no restriction in the muffler but I would definitely hesitate to try to bend the core insert with a plyers to quiet it. As you said just adds restriction to that design. I just wasn't sure of the db level and don't have a meter. The bike runs fine with it (FMF) and I feel it has plenty of power. It is quieter than stock YZ but noiser than the WR. I just do not want to get to a forest, etc. and they tell me I am too loud. Although, I know of no place that they currently are doing this in CO.

What about that stock WR? That resistance is surprising. I just looked at the Promotobillet insert thread and from Lorenz's picture that he implied that the exhaust is flowing through the grading and not a lot from the two tubes?


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