How Much Quieter is the FMF Powercore 4.1 Slip On w/ Insert

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2/6/2020 8:29 AM

My '12 YZ250F has a FMF Powercore 4.1 with the stock head pipe and it is too loud for me to ride in my area. Before I go and order the quiet insert, can anyone tell me if it makes the bike much quieter? I read mixed opinions on if it actually makes a difference. Hopefully someone here has some experience with it.

Would I need to re-jet after the insert?


2/6/2020 3:45 PM

Can I ask what exactly is "too loud for me to ride in my area"? Is your track or park ranger measuring exhaust noise levels? Or do you have neighbors complaining?

If you just need to pass sound tech, I would ask FMF directly. They test all this and should have a clear answer.

If you have complaining neighbors, I would expect a silencer insert to be about as effective as turning a guitar amp down from 10 to 9- probably not the solution.

Hope this helps. Let me know if you would like a translation of decibels into English.


2/6/2020 4:10 PM

I have a quiet insert on a 2012 WR450. Obviously not an apples to apples comparison but close.

It made a slight difference. Nothing major. I would say maybe 5db. More then anything it changes the tone. It removes a lot of the high end out of the sound and makes it more throaty. For the price, it's worth the shot to try it out.

I don't think it would require any carb tuning.


2/6/2020 9:50 PM

I had a Q4 on my old Kawasaki 250. It was designed to be quieter than anything else they offered, but I live in a suburban area and my trails run real close to subdivisions and houses.

Q4 alone was not quiet enough. Bike still had a pretty loud mid/low tone off idle, and it just exploded when you really got on the throttle. Not good for stealthy riding.

I got their quiet insert which took me down to 7/8" opening at the end. It took a bit of the obnoxious roar off, but it was still pretty loud to my ears.

Ended up selling the Kawi and getting a KTM EXC which is quiet like a sewing machine with their stock muffler in place.

If the tip isn't that expensive you could always try it out and see. I'm not sure who if anyone makes decent performing mufflers/exhausts that are as quiet as stock or quieter. You could try the FMF Q4 like I had... it's absolutely quieter than the Powercore, but how much so is subjective.


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2/12/2020 6:56 AM

msp332 wrote:

Can I ask what exactly is "too loud for me to ride in my area"? Is your track or park ranger measuring exhaust noise levels? ...more

I have a small backyard track on the edge of a residential area, The closest track to me is over an hour away so I try to be very conscious of noise/dust etc as I know how lucky I am not to be able to ride where I do.

I recently bought the bike with the FMF on it and before replacing it with a stock pipe I wanted to try the quiet core to see if it made a difference.


2/12/2020 8:11 PM

I have a 2019 KX450, so it isn't a direct comparison, but I tried the 4.1 first without the insert and it was shockingly loud compared to stock. I took the insert to the track with me the first time I rode with it (mine came with it), just in case. The thing was so loud while riding it was almost distracting to me. I put the insert in and it was much better, and with my bike the added back pressure actually gave back some of the low end that it lost without it. It was less free-wheeling though (the engine braking was more like the stock system). I don't know if the same effects will occur on your bike...YMMV.


2/12/2020 8:40 PM

They do help. Takes it from absurdly loud to almost reasonable...


2/13/2020 9:15 AM

Thanks, guys. I've ordered the insert since it is simply too loud currently.