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How does the FMF Q work on the 07 450f?

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I have to quiet it down, no ifs, ands, or buts about it. I ordered a FMF Q from the dealer late yesterday but want to get some feedback from people that have used them. Doing some searching on here I read a post that the fitment sucked and that they had to send it back? And does it tame the sound down pretty good? And how much power loss do you feel? Need some input on it just in case there's a better alternative out there so I can cancel my order early tomorrow morning before it ships. Thanks.

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My son started off with a Q4ti and it was pretty good but it has a baffle right in the middle. That baffle diverted gas out into the packing and blew it out in about 10-15 hours. He is now using a Powercore which just has the SA screen at the end. It blows 96db, the power is a little better and it doesn't kill the packing real quick. He was going to try the 4.1 slip on but they were out of stock when he needed it! We've since refurbished the Q4 and are saving it for emergencies.

CR

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Threw a FMF Q4 TI on my 07 not only did it quite it down I've picked -up better throttle response means less clutch activity and additional 5mph on top
Interesting. What altitude, temps, humidity and jetting you using?

I'm thinking this means you were previously jetted too lean with the stock muffler. Eg. Previously too lean on the slow jet if you'd gained response on initial roll open with the Q4. And/or previously too lean on the main jet, if the Q4 gives more power at wide open. Not trying to make an argument. Just interested, since I swap mufflers a bit, and I find that wrong jetting makes more diff than a muffler swap.

FYI: I know the owner's manual and various FCR tuning guides say the main jet has no effect below 1/2 throttle open, but in my experience with the FCR40 on the 06, the main seems to effect down to 1/4 throttle.

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My son started off with a Q4ti and it was pretty good but it has a baffle right in the middle. That baffle diverted gas out into the packing and blew it out in about 10-15 hours.
Hey CR, have FMF placed a cone baffle in the middle of the Q4, or just a flat disc in there or what? I've got a Q2 Ti, which I've thought about rebuilding inside (rear half) since it never flowed particularly great.

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The Q4 is a very decent muffler. I had one on my 06. It is just a little quieter than the stocker without the spark arrester and noticeably quieter with it inserted. Has a nice tone when compared to the stocker. Power was about the same either way. All ya need is a little permatex when installing it as it does not require a clamp setup like the stocker.

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Hey CR, have FMF placed a cone baffle in the middle of the Q4, or just a flat disc in there or what? I've got a Q2 Ti, which I've thought about rebuilding inside (rear half) since it never flowed particularly great.

Sorry, didn't see this until now! The Q4 has a baffle right in the middle. It's flat but has holes in it simillar to the tube. I guess it is supposed to divert more of the exhaust out into the packing. It's works, but blew through the packing pretty quick and turned the can blue fron heat. Good thing it was a titanium can, it might have burnt through aluminum. I thought about drilling the holes a little bigger in the baffle to help with the problem. However, right now, we're just using that silencer for a backup or incase the other one fails tech inspection (97.5 db).

Mike

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We've been using the Q4 for a couple years now, when we ride off-road. It tested 93db last weekend, after about 25-30 hours on the packing. There is a noticeable drop in power from the stock system, especially on the top, but power at the bottom is still very good and response is very good. I would recommend the pipe to anyone riding off-road, but keep your stock system for MX.

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hello, one stupid question, does Q4 muffler fit to original header, of does that required FMF power/mega bomb header?

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You could check their website for specs. in my experience all their "slip-ons" will fit stock headers.

With more restrictive mufflers, like the Q4, the power reduction is always worse than it need be, unless you modify the jetting to match. With a jetting change you get a lot of power back for whatever throttle opening need fixing.

Of the course the opposite applies too. If the original jetting (or EFI map) was too lean with the open exhaust, then the quieter muffler can sometimes make the power feel better/broader.

Kevin, assuming you have a carb, did you try going one size leaner on your main jet?

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hello, one stupid question, does Q4 muffler fit to original header, of does that required FMF power/mega bomb header?

Yes if you buy the right year model it just slips on.

I had one on my 2007 and it was way better than the stock and quiet to boot.

I had to take it off after running it for two years and 90 hours and immediately noticed the difference when I put the stock back on. Less power with stock.

Now if we could just get the factories to make something similar for stock. One less thing for the dirt bike haters to complain about when they try and shut us down.:banghead:

2007 KX450F = 92db

2009 KX450F = 91db - tested 2 days ago.

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Less power with stock.
If you felt the stock muffler reduced power output compared to your Q4, then quite likely you need to richen your jetting with the stock muffler on. Which jet I dunno, that depends on how much throttle you have open when you think it feels flat.

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:excuseme:

Threw a FMF Q4 TI on my 07 not only did it quite it down I've picked -up better throttle response means less clutch activity and additional 5mph on top

not to be a nit-picker here, but I know you did not pick up an additional ANY mph up top. These bikes have enough power stock to wind out the gears.. The bike could have 300 horsepower and the top-speed will remain the same unless you change the gearing (with sprockets) or raise the rev-limit with electronics. Its how cars,trucks, anythings with motors and gears work.

The only way a pipe would give you additional top speed would be if the motor didnt have enough power to overcome resistance and top the motor out... However, these bikes, bone stock, have plenty of power to hit the rev-limiter in fifth gear, with any gearing configuration you can fit on the bike.

A pipe that yields more horsepower will get you to topspeed more quickly (read faster acceleration) but it will not give ur more topspeed. Just a lil FYI.

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If you felt the stock muffler reduced power output compared to your Q4, then quite likely you need to richen your jetting with the stock muffler on. Which jet I dunno, that depends on how much throttle you have open when you think it feels flat.

You are right.

I ran the Q4 on my new 2009 today and I think in need to get a hold of a programmer to get back the FI snap that I was used to.

What do you think I should do to try and return the hard hit I have become accustom to with the stock exhaust?

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What do you think I should do to try and return the hard hit I have become accustom to with the stock exhaust?
I'm confused. I was referring to the jetting on your 07 (too lean for the stock muffler so the Q4 felt better). If the Q4 felt more responsive on your 07, then your 07 probably had much untapped throttle response with the stocker - had you richened up the jetting (and maybe the leak or AP screw too).

Not sure what you mean if you are talking about your 09. Many threads on the 09 EFI. I don't take careful note of the comments on the EFI, but I think people say it has the slightly lean map enabled by default. If true, then the Q4 on the stock 09 might be a good pairing. But I'm not sure by any means.

My moral here is that if you jet/map for the exhaust, then the results can be unreal.

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I'm confused. I was referring to the jetting on your 07 (too lean for the stock muffler so the Q4 felt better). If the Q4 felt more responsive on your 07, then your 07 probably had much untapped throttle response with the stocker - had you richened up the jetting (and maybe the leak or AP screw too).

Not sure what you mean if you are talking about your 09. Many threads on the 09 EFI. I don't take careful note of the comments on the EFI, but I think people say it has the slightly lean map enabled by default. If true, then the Q4 on the stock 09 might be a good pairing. But I'm not sure by any means.

My moral here is that if you jet/map for the exhaust, then the results can be unreal.

I was referring to my 2009 that I was riding today.

The Q4 has taken the punch out of the motor and I want to get it back. So I think that it may be time for a EFI programmer.

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