Question about quieting the exhaust (really)

I realize this is blasphemy, but I have a question about quieting down my WR426.

I bought it with a White Bros E-Series exhaust. But I also got the stock headpipe and muffler on the side.

It appears that there are 7 discs in the muffler now. I have two extras. Would I get any significant lowering of noise with fewer discs? And how many can I go down before losing a lot of power?

Also, how bad (good) is the stock exhaust system for noise and power if the black insert is removed? I assume the screen stays in?

It has supposedly been rejetted for the larger headpipe and muffler, but I assume that it would maybe run a little rich at worst with an unplugged stock exhaust.

I want to do this because an upcoming trip is sort of low performance.



I ran 3 disks on my 98' WR400 E-Series and realized moderate loss of power in the midrange. The top end was noticably less, but what was anoying was the sound. It was a definite high "pop-pop" instead of a low thumper sound. After that ride in Moab I sold the E-Series, put the stock pipe back on, and ran a Thumper Racing insert. In addition, the E-Series melted my rear fender and I had to invest in a heat shield. Now I run the Q-Series on the WR450 and live with whatever it brings.


Not sure about the WB system. Stock muffler without the baffle is very loud. With baffle very quiet but no performance. Alot of TTers including myself run stock pipe with an aftermarket baffle. Its a good compromise in sound and performance, most sound test at about 92 db. Costs range from 40.00 to 90.00. Do a search and you will finds lots of info., its been discussed recently. Pipes do effect jetting. With an aftermarket baffle you can run close to stock jetting. Open pipes need richer jetting, more inline with YZF jetting.

I was scanning a 2001 Chapparal catalog, and they show a Exhaust Quiet Core Insert for the E-Series.

Has anyone tried this? Seems easier than changing back to the stock exhaust.

The quiet core for the e-series is a joke dont wast your money it doest do much at all. :)


If you're really serious about quieting down your bike, put the stock muffler back on and get one of those GYT-R inserts. Mine measures about 87 dBA at idle and 96 dBA at about 4k rpm, which meets most noise standards for off-road bikes. If you jet it properly, it will be a runner and the trade-off in power is worth the reduced noise. I've got one and am happy with it and a friend with an '01 WR426 put one in his with stock jetting and is also happy with the performance of his bike.

I put my stock back on with a PB insert, ran terrible with the high boy pipe. Went down to 6 disc's and a quiet insert in the WB and its quiet enough now.

I had an E series S bend shorty on my 400 for about one day of riding. It seemed loud no matter how many discs were in it, but that might be just because the sound resonates right into your helmet instead of the rear of the bike. What a P.O.S.

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