Require QUIET exhaust system for CA, Please assist.

In search of a 98db solution but would like to retain performance.

I went to Georgetown on Friday and was harassed again. I should have known better, I raced the Fools Gold Enduro there in May and was required to run my CORKED stock pipe... :)

My White Brother’s R4 tested off the pipe at 106db.

My uncorked Stocker tested 102db and 98db corked.

My buddies ‘02 YZ426F with FMF Q and Powerbomb header tested 101db.

I need a "Confirmed" setup that will test under 100db and according to the Ranger it will need to be at 98db for the 2003 race season...

Does anyone know if rubber mounted bars and anti- vibration bar inserts can contribute to a false RPM/DB test result...?

Any assistance would be appreciated.

I seriously question 98 dB with the stock corked exhaust. That should be in the upper 80's, maybe with your mods (airbox lid, yz timming), barely into the 90's. I highly suspect the accuracy of the testing.

That ranger is testing incorrectly. If that reading on the stock corked pipe where correct, the bike could not be legaly sold in CA. Go to the BLM and get a copy of the testing procedures and make the ranger follow them. He is either grossly misinformed or has an agenda. In CA, i would guess the latter. If you stuck the corked pipe in your ear and ran up to 10,000rpm, you might hit 98 db.


Jason I just my WR400 tested at stonyford with stock EX, and it tested at 92db, somthing is wrong and i uesd a TTR250 baffle in the stock muffler (the out let hole is 1in. and the WR is 1/2in) if it was ranger DICK at G-TOWN then that is why you got a fales test.


Try a Vortip or Baja Baffle insert on your stock exhaust. Both run at about 94-95dB. Very quiet, while still retaining good power.

The new BRP Top clamps with rubber mounted bars works great. What a difference front the solid mount. You might not think so but my wrists feel great after a ride, not as much fatige.

Were you on the bike during testing?

Having the motor noise sheilded by your legs matters.

Having a consistent testing regimen is perhaps the most important thing that would come from all these inconsistencies.

You might want to look in to a CRD exhaust system. They advertise this system at 91 db. A buddy of mine bought one of these and it is the quietest system that I have seen. Now he just got the system and it doesn't have 1 hour on it so I can't give you a opinion on it after a few rides. I quess this guy claims that he will stand behind his product. Anyhow I am going to check it out after I get my broken ankle healed up. I have an E-3 on my wr400 and it is way to loud. I don't want to bring attention to my self when I am ridding. This is the website:

There is a advertisement in the July Dirtbike mag on pg6.

Unfortunately the CRD International system is not as yet U.S. Forest Service approved. They are in the process of getting the approval now, but who knows how long it will take is any ones guess.


Just a bit of info, I was tested at Stoneyford (Rangers are alot friendlier there then Georhetown)earlier this year and tested at 98.9

That was an 01 WR426 grey wire mod, airbox top removed, stock timing, stock header, WB E-Series freshly repacked with silent sport packing and 8 disc.

Had my Husaberg 02 FE501e tested stock 91.2 at Hollister last weekend. They were doing a vollentary testing and if you passed you got a special sticker put on your green or red sticker to notify other rangers that you past testing. This sticker is good for the same amount of time as the green sticker. If you get retested and they find you have changed exhaust you can get fined.

Good Luck

Ride Safe, Ride Often & Have Fun :)

I've been tested twice at Middle Creek on my '99 WR400 w/stock exhaust & Thumper Racing Quiet Core. First time was 95dBA, second was 96 dBA - was ~9 months between tests and I've never repacked my exhaust.

Something is very wrong with the test procedure or equipment for a STOCK exhaust to be measured that high.


I really think it is the rubber mounted bars and anti-vibration inserts... A "wire rpm gauge" is placed on the bars to indicate a certain RPM when a corresponding amount of vibration is reached for the DB test. I think the rubber mounds and inserts are dampening the vibration resulting in an inaccurate test. More throttle is required to reach the corresponding RPM. The Ranger at G-town must have had my bike at mid throttle. I was asked to get off the bike and hold it upright as a second Ranger worked the throttle. This was the procedure for both tests at G-town.

Matt at Stonyford tested my bike in March with similar results, at the time it was just sampling, not a requirement. My uncorked stock still exceeded 100db

I really need to find a resolution in order to continue racing District 36 and riding in Nor Cal. G-town, Wilseyville and Foresthill are all testing recreational riders now and require 101db or less to ride. No Pass, No Ride....

I appreciate all your comments.


Ride safe, Ride another day...

I 100% agree with the CRD system. I have one on a KTM right now and I can't say enough good things about how well it works for such a quiet pipe! It has a super clean polished finish and has over 60 hours on the bike with no sound increase.


The tach they used at Middle Creek last year was set on the flat of my rear fender. I don't remember what tach they used at the Sawmill but I suspect it was the same - set on rear fender. I know they didn't use a clamp on the plug wire.


jason check pm.i didnt realize you live in antioch,i have a few friends who live there and work near me .so maybe could give pipe to them and save shippng plus i could it get back to you 1 or 2 days max.


By Bill Dart, AMA District 36 Legislative Officer

...the popular Yamaha 400/426 series. While right on the margin of legality, they are still too noisy right out of the crate. But the problem really gets bad when an aftermarket exhaust system is installed, which it seems about 90% of these bikes have today. Dirt Rider magazine did testing for power and sound levels on all of the popular exhaust system available for the Yamaha 400/426 series, as well as the new Suzuki DRZ400. According to their testing, the Yamaha measured 100 db stock, barely within the 99db, plus or minus 2 db, mandated by California law. But none of the aftermarket pipes tested came in below 102db, and most were between 104 and 106 db. This means that NONE of the aftermarket pipes for the 400/426 are legal to use anywhere on public lands in California, not even for racing.

It is possible to recieve a 300$ fine for a non USFS stamped silencer.

Our friend Ranger Matt at Stoneyford was kind enough to let me put my stock pipe back on my bike.

I had an Arrow that was quiet and I had put a sparky core inside of it for a SA.

No stamp, no good.

I won't try that again.

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