Exhaust system endorsements

I bashed my stock header in from a crash, and I want to replace it with an aftermarket unit. I've done a search, but I'm not really sure what the best system may be for my WR. I'm not terribly concerned about noise, I want to keep the bike's performance but it would be nice it if it were quieter than my uncorked stock unit.

I've been looking at the Pro Circuit T-4 tuneable system, can anyone let me know what you think of this system? Also, if you have had success with another system, please let me know.

Thanks to everyone for your help! :)

Ya better be concerned about noise :D

There is a mjor crack down on noise on your local OHV parks..

Personally I like White Brothers, either or the E series of the R4. Why? The Bike Came with a WB R4 :)

Others will explain there resons I have no prefreance either way....

But Noise ya better make sure you can get the beast down to 98db or you dont ride

DMC Alien

Originally posted by Scuba Steve:

I've been looking at the Pro Circuit T-4 tuneable system, can anyone let me know what you think of this system?

The T-4 “tuneable :) ” system is well designed, well made, very strong yet light and in my experience very durable. But it may be the loudest aftermarket silencer you can get, although most others are right there with it in the noise department. It will make your head hurt. I had to take mine off because the header will not clear the petcock on my Acerbis tank, this is probably true of most aftermarket headers.

I have a very low opinion of FMF products, I don’t like the rear mounting systems they use (the ones I have seen, anyway). On the other hand some folks don’t like the fact that WB stuff requires the stock header to collector gasket.

A lot of people on this board have raved about the Dubach products, I’ve yet to see one. Another new and popular offering is Thunder Alley, a one-man shop in CA. If you like handmade, steel, reverse-cone megaphones (the stock WR can is a reverse cone meg, the only other such design for these bikes) that is the pipe for you. I’ve got one, it is very loud, it works really well in lower and mid rpm ranges but didn’t seem to rob as much top end as my T4 or my buddies WB R4. BUT, the megaphone section sits very close to the side panels and is melting my sidepanels (and preprinted numbers :sad: ), so I typically will run the stocker until race day (off road, I need a spark arrestor).

So, to summarize, I have a significant # of hours under my belt with the stocker, a T4, Thunder Alley, an FMF Q (piece of junk, but a quiet piece of junk), and the stocker. I’ve got a few hours riding a Yosh, a WB R4, and a stock WR uncorked.

After reading your post again my advice to you is to locate a stock header and a YZ silencer. Unless you need a spark arrestor I predict you will be happiest going this route.

Hope this helps.

My PRO-CIRCUIT -T-4, works great, but it is loud, and I put the 1 3/4" end cap ( better mid range), workmanship is first class. Mike

I have the T4 on my 99 WR and it is very loud. The 2" end cap makes power mid to WOT, the small 1 1/4 (I think that is the small cap) makes good bottom end power. I also am trying the quiet core insert. This ammounts to a cone shaped spark arrestor screen with a plate welded on the end with a small hole that has a tube welded to it. It has a strange pop-pop-pop sound at idle but is still pretty loud when you open up. This pipe is a substantial weight savings over stock but have to admit anyone within 20' behind you will feel it blasting at them.

The headpipe is very close to the underside of the coil and you may have to bend that small slip on connection wire up a bit so it doesn't melt the plastic cover.

[ June 07, 2002: Message edited by: Mike from WA ]

Thanks everyone! I asked some of my riding buddies the same question, and several of them liked the Yoshimura system a lot. Hick mentioned it, does anyone else have an opinion?

Thanks again to everyone for your help! :)

The Yoshi is about the second loudest I've heard, the DSP is by far THE Loudest!! I run the stock YZF with a Pro-Moto Billet S/A. It is surprising to me and others how quiet it is. No where near as loud as a stock un-corked WR, and the S/A seems to really tone it down from stock YZ.

My .02


Hey Hick, I recently bought a 00 WR426 and it runs great with an WB E Series but it's WAY too loud. Your post concerns me though because I have a FMF Q sitting in its wraper in my garage. When you say it is junk do you mean power wise or in its construction?

I know I could take some disks out of the E Series to quiet it down, but my experience with my XR 400 is that to make a substantial difference in noise I had to drop from 10 to about 4 disks, at which point I was not making any more power than stock.

So, I might just leave my White Bro's on and be offensive to the world. And myself.

Thanks in advance!


Are you guys that are having problems with the FMF Q doing a lot of jumping? I've had mine for about a year now with over 1000 trail miles on it, and I have not had any problems, and have been quite happy with the power. I think it woke up the midrange on my YZ timed WR, at least over the Supertrapp IDS with the quiet core. I would compare the sound level to a stock KTM RFS exhaust.

I have the Big Gun header / muffler, sound is rated with the quiet core & 1 1/2 end cap @ 97-98dB. I have dealt with them 2X & their service was great. The tapered head pipe clears the petcock on my IMS tank. I know they are a little pricy but their craftmanship is excellent & extremely durable.

Originally posted by XVWDVW:

Hey Hick, I recently bought a 00 WR426 and it runs great with an WB E Series but it's WAY too loud. Your post concerns me though because I have a FMF Q sitting in its wraper in my garage. When you say it is junk do you mean power wise or in its construction?

In its construction. Power wise it tamed that YZ mid-range hit and seemed to kill a small amount of bottom. It also needed a leaner pilot jet in my case. It still revved well, the best I can describe it is it walks briskly up to the rev limiter, while the stock YZ can tries to run through it. Unlike my PC T4 it was still an enthusiastic and willing revver, so if that is your style you may like it even better, but I can’t say I was disappointed in the power, especially considering the low noise level. I ordinarily like to ride a gear tall and lug it, but I was perfectly happy to race my bike off-road with the Q pipe and that kind of power, it may even add to my stamina, but guys who moto may not want to lose that mid range snap.

But if you haven’t already noticed the Q is big and long. I don’t think it is necessarily heavier than a stock YZ can, but its length extends well beyond the rear mount and this adds leverage to that weight. And because the rear mount isn’t fixed rigidly to the can it will tend to want to rock to and fro about that axis, eventually elongating, and in my case ripping out, the four (small) screws that secure the can to the collector.

I wish I’d never bought one, but if you don’t want to, or cannot, return yours then perhaps with diligent installation and a little vigilance over time what happened to me won’t befall you.

To ensure a good install I would tighten the header, the lower subframe mount, the header-collector clamp, THEN the rear hanger thing. Then, perhaps, if you keep a close eye on those four little screws things will work out.

I, however, wouldn’t bet on it as I noticed the problem with this thing fairly early on, and in fact had reapplied loc-tite and tightened up everything just a few hours before the holes, which were getting slightly elongated, ripped out completely, first a few and then a few more until it was all gone. Unfortunately this happened in a race or I would have recovered the parts (couldn’t find it w/ the sweep riders) and fixed it.

Ideas for a permanent solution to the problem would be:

a) Just weld the damn can to the collector :) , but this would probably hamper repacking since I believe the packing needs to come out that side.

:D Introduce a few extra holes and screws to make the can-collector connection sturdier.

c) Fabricate a solid rear mount and weld it to the can.

Hope this helps.

The trick in getting the e-series past a sound inspection at a race is to go to the Tech Inspection with 5 disks installed which will bring the sound level down to the 98db acceptance level. Then go back to the truck/trailer and change it back to 12 disks. If you use anti sieze compound on the threads you can change them as much as needed without messing up th bolts or the threads.

I also keep an allen wrench in my fanny pack just in case I ever get one of those "On the Trail" inspections.....I'll just change it out there, pass the inspection and swap it back on down the trail somewhere.

I know, I know...."Thats Cheating....I'm going to hell...I know...

Bonzai :)


I just ordered an E-series S bend. Does it come with 12 discs? I need to know so I can order more if I need them. Also does it make the bike run a little rich or lean? Thanks!


I have the FMF Power bomb with the Q series Muffler. It works great. It is huge :) but it works well. The power is about the same as stock. I do feel a difference in the mid range but it only makes it better. I have always liked the quality of FMF.

i have wb e-series promeg and its great silencer except too loud.people are having trouble passing sound test with it,i personnally havent been tested but with 8 discs i doubt i'd pass.the silencer that seems to give best perfomance while still remaining quiet enough to pass sound db. test is FMF "powercoreIV Q".if you live in calif your going to have to deal with sound issue sooner or later,so you might as well spend the money on silencer that will pass now.otherwise you'll be like me and a lot of other people spending $300 on new quiet silencer and stuck with $300 silencer that you cant use anywhere.there pretty serious about enforcing this law,i doubt its going to fade away.

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