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rdefonce

'08 YZ450F stock muffler or FMF Q4; which runs better?

7 posts in this topic

Guys, I may have made a mistake buying a Q4 for my 450. I was going to use it with my Megabomb header BUT after trying to separate the header/midpipe on Megabomb, it won't budge!

I'm not going to separate it because it's only for one week that I need to keep my bike quieter, as I'm going back to Megabomb header/4.1 muffler after week is over.

That said, I'm just going to use my stock header, either with Q4 that just bought, OR with stock muffler (which I've heard is quiet, but I have never ridden with it)

I assume the stock muffler is fairly quiet, but would it run as good (or nearly as good) as with Q4?

Thx!

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The stock muffler is fairly quiet and if you have the stock jetting it should run pretty good, depending on altitude. How do you like the megabomb/4.1 set-up? What jetting are you running with this? I was thinking about upgrading to this exhaust on my 08 450f .

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The stock muffler is fairly quiet and if you have the stock jetting it should run pretty good, depending on altitude. How do you like the megabomb/4.1 set-up? What jetting are you running with this? I was thinking about upgrading to this exhaust on my 08 450f .

Wow, guess I should not have bought the Q4 since the stock pipe is quiet. Well, I'll probably be selling a brand new Q4 soon . . .

About the Megabomb/4.1, it works very good on the YZ450. You would like it alot. Hate to admit it but I haven't been in carb since I purchased bike used so I don't know for sure, however the previous owner said 1 size richer on most circuits.

Tested on a KX450F in Dirt Rider, they raved about the pipe, saying it worked better than any other aftermarket pipe they tested (on a KX450, that is)

I set needle clip 1 richer than stock #3 position, and turned fuel screw to about 1.75. Was set at 2.25 when I picked it up, too rich!

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The stock pipe really isn't that quiet, I believe it's about 97 decibels? I bet the Q4 will make a good bit more power, the way the stocker chokes it off...

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I would keep the Q4 and use it. I needed to buy a spark arrester for riding in the forest and just could not live with the endcap version for the stock exhaust. Also like to keep my bike as quiet as possible without sacrificing much power. With the Q4 I have way more midrange, bike revs clean with a strong hit on top. Whats not to like? If the Q4 will run stronger than stock thru the whole rpm range and sound good, why would you go back to stock?:thumbsup:

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If the Q4 will run stronger than stock thru the whole rpm range and sound good, why would you go back to stock?:thumbsup:

Mainly to save the $, since I would only be using a "quieter" setup for 1 week out of the year.

Back home I mainly only ride on closed-courses with the 450, so I use my Megabomb header/Factory 4.1 muffler combo. (Got my little 200 smudgepot w/spark arrestor for National Forest off-roading)

HOWEVER,

Since you and "theuberacer" say how much better the Q4 runs than stock, I think I'll bite the bullet and run the Q4!

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Yep, need the spark arrestor to be legal, bought the Q4 slip on. Bottom line, VERY quiet with the sparky in the Q4 but power is softer than stock, or at least no stronger. With the sparky out runs stronger, smoother and louder but not amazingly so. It is nice but it is NOT a racepipe. Big can too, looks a little goofy after the stock shorty.

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