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WR250F Silencer on a YZ250F

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Anybody know if a 2008 WR250F silencer will fit directly on the 2008 YZ250F bike. If so will I have to revise jetting or will it just run a little rich? I need to get this bad boy to quite down for some local trail rides I hope to partake in and the Q4 may not be quite enough.

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I'm not sure about a 2008, but I can tell you that on the 07 models, the WR muffler does not fit the YZF stock head pipe. Head pipe size and length is different. I have not tried swapping the whole system, but probably if we swapped the YZF header and the WR muffler, then we'd have a system which fits.

The Q4 is a pretty good product- it performs great and it is pretty quiet. The Q4 makes a stock MX muffler seem like it was only meant to annoy the neighbors. Don't get me wrong, a Q4 is not a WR muffler though. I'm not sure if your club uses the same measurement system as the AMA's procedure. The AMA sound measurement is going to go something like this- Stock WR muffler with the little corkie removed- 89 to 90ish DB = pretty quiet indeed. YZf with a Q4 = 93ish. 3db = twice as loud, so a Q4 would be enough louder than a WR muffler.

Hope this all makes sense and is helpful info.

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Your information has been very helpful. I will discontinue searching for a WR250 silencer now. I have been told the sound test we use is a SAE J1287 and according to my source its commonly called "the 20 inch test". I am not sure if this is similiar to the AMA testing. I am thankful for your anticipated db levels. Do you happen to have an idea what the YZ250F will produce in the stock form?

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Skidoorules,

Glad the info was helpful. That is the same test we use here (20" away at 5500 rpm). Guys with a Q4 on their YZ250Fs were commonly reporting 93db last summer. I didn't put my Q4 on until later in the summer and so I didn't test with it. I had been running a Q2 which was barely passing the 96 test- it was more like 97, but I'm sure my Hotcams added a db or two.

A stock YZF muffler would probably test about 99 or 100. I have NO idea how the magazines come up with their sound test numbers because their numbers simply are not correct.

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