Discs needed to pass sound test

Anyone with an E series disc system advise on the nuber of discs that I need to pass a sound test for a ride (Ca forest) no I dont have any idea what the DB level is they didnt post it on the flyer... 2001 WR 426... Thanks in advance for your help...

I think the limit is 98dB +/- 1dB - I might be wrong. I think I read somewhere around here that a guy was able to get down to 98dB with 6/7 discs. I think you're going to be hard pressed to get the E-Series to pass the sound test :)


Actually, I think it is 101db for off-road. You should be able to pass easily with a WB E-series. The problem will be that if you remove disk to make it quieter you may need to check your jetting. I put mine down to something like three or four disk and took it up to Mammoth Bar. Of course, they didn't even check it. But, that may be because it was so quiet. I did notice a big power drop and some missing like I had a jetting problem. The next day I kicked it back up to seven disks and it ran fine. The ideal situation is to test this stuff ahead of time so you can get your bike dialed without too much sacrafice in performance. It can be done though. That is one feature of the E-series exhaust systems that I really like. Good luck, Paul :)

All right, here is an AWESOME trick to pass a DB test, get a couple high strength hose clamps, you can usually get them at a diesel supply store. They are usually installed on turbo and intercooler connections. They have no holes in them where the threads are. Put these clamps over your discs to basically cover the openings between the discs. After you get sound checked, slide the clamps off, and you are back to normal. With an E series you should probably pass anyway.

The current requirement that the Forest Service is using is 101 decibles. They were checking each and every bike at our Cowbell Enduro at Upper Lake, this past Saturday. About 20 bikes were disqualified. Many were WR's.

I have a W-B E-Series and just recently started experimenting with their quiet core insert. I was running 8 discs, so I just tried the core with 8 and found that the bike was almost as quiet as a stock CDN. pipe but the power and throttle response were all but gone. I quickly added 4 more discs and found that the sound level did not increase that much, but the power was quite a bit better. That is as far as I got with it, and as it stands now, I can't imagine there would be any sound test that it would not pass. I do plan on modifying the quiet core by drilling out and/or removing some of the restricting plate washers. Hopefully that will put the power back near where it was without upping the noise to the point where I draw fire from the "sound sensitive" people out there.

[ November 08, 2001: Message edited by: Pete Z ]

For some reason I had 98dB stuck in my head. Last time I had my WR at Middle Creek we got sound checked as a 'courtesy'. I passed no problem at 95dB but I run a stock '99 WR silencer with a Thumper Racing insert.


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