2000 WR400F FMF Powercore 4 Universal Exhaust - Silent Insert Options



I was given an exhaust for my WR400.  I installed the exhaust and, no surprise, the bike is quite loud.  Previously I was running the OE exhaust that was gutted (I bought it gutted) and a PMB silent insert.  This resulted in an acceptable noise level to me.


I installed the FMF exhaust because it had a S/A, which my OE exhaust didn't.


My question is: I'd like to install a silent insert in this FMF exhaust, but I can't see a way to do it.  From what I have researched it seems there were different models of "Powercore 4" and the universal one I have doesn't seem to accept a silent insert.  It seems the S/A screen is welded onto the muffler core.  Also, there is no hole in the end cap that would accept a set screw like it seems the Silent inserts required.


Am I missing something?  Is there a way to install an insert in this model exhaust?


Any recommendations would be great.  I love the sound of the exhaust, but i'm just trying to be a good neighbor.



Could you measure the outlet diameter and then order a db dawg that would fit?

I don't see any fiberglass packing.  That may be your noise problem.

I don't see any fiberglass packing.  That may be your noise problem.


I don't know if this facetious or not.  That picture is of the exhaust torn down while I was repacking.  I installed a fresh FMF packing kit.


I've never heard of the DB dog.  That could potentially be used, but it would require the removal of the current S/A screen.  Thats not the end of the world, but id have to figure out how to implement a S/A somewhere else.

What insert did you run in your stock exhaust? My 426 is too loud, has the stock exhaust that the previous owner gutted. 

Rob28x, I see that you live in Michigan so therefore if you are on the trails you need to comply with the 94dB sound limit, no idea what laws are on the track.  


With a stock exhaust that is intact, the only tip that I knew of that could drop below 94dB was the White Brothers Vortip, which is no longer available from the manufacturer.  The Yamaha GYTR tip only reduces the sound to 96dB, so it is not compliant with Michigan laws.  


The FMF Q slip-on exhaust does have a spark arrestor and can get you below 94dB if packed properly.

Thanks for the info. I have a GYTR insert coming already for the bike. I am sure it will make a big difference over how it sounds now.

Sorry for the late reply. 


In my stock WR400 exhaust I had the Pro-Moto billet insert, which I affectionately refer to as a "butt plug" . My subjective opinion is that it made a good improvement at/around idle.  But once you were up in the revs/had the throttle open it wasn't a whole lot quieter.  Again, I didn't measure this in any way.




I have ridden the WR at The Mounds ORV Park near Flint with the gutted stock exhaust and I didn't get any flak for it.  But, it was off season (New years day) so I don't think they were paying too much attention.  I imagine I could go there with the FMF exhaust and as long as I wasn't revving like crazy in the parking lot I would be Okay.


Id like to get a quieter solution mostly because I street this bike and I live near downtown Royal Oak.  I'd like to try to be a good neighbor.  "Passing" the DNR regulations would be a nice benefit although I will mostly trail ride on private property.

Edited by gilkeyb

My GYTR insert came on Friday. It made a huge difference imho. I have only ridden it around the neighborhood as I just got the bike up and running but I was most impressed the difference it made. But I only heard the bike running with an open exhaust and never was able to hear how it sounded stock to compare.

The other issue for me with the PMB insert or your GYTR insert is that it leaves you without a spark arrestor.  This makes you, technically, not legal to trail ride here.  I never came up with a solution for that.  

Yeah I didn't think about that. Wonder if you could take some small pieces of aluminum screen and some hose clamps to attach it around the tubes where it goes inside of the muffler?

I tried to put some aluminum screen door material on in a way exactly as you described.  It was gone within 5 minutes of riding (melted I think).


If you had some steel screen that could work. But definitely you need something more robust than aluminum.  I only tried the aluminum out of desperation because I was riding at a place that required spark arrestors.  Fortunately I wasn't checked that day

Try a stainless steel Drain screen. I had a white brothers pipe on a quad that has no SA when I got it, could not get parts so I went to a home depot and found a drain screen , modified it to work and never had any issues with it.

Took the bike to the first track day this year with the FMF exhaust.  With this exhaust, my bike was still one of the quietest bikes on the track.  A few of the 450s were brutally loud.  And you could always hear where the guy with the CR500 was.


I guess it could be worse (louder).  My neighbors will have to deal with it!



Edited by gilkeyb

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