noise & distance

2 replies to this topic
  • MXOldtimer

Posted October 08, 2000 - 06:33 PM


I got a flier for the Monkey Butt Scrambles and since I haven't been off a MX track in a few years it sounds like fun.

I need some info

They are calling for a 99 db limit , what does the 426 with stock pipe put out ?

How many " racing " miles can I expect out of the stock tank ?


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  • Hick

Posted October 09, 2000 - 06:35 AM


In the Dirt Bike test the stock ’00 YZ pipe made 102 db but I guess this would vary depending on how the test is conducted. I think their db test was with RPMs at half of redline with meter like 10 ft. back. I would call the promoter and ask if your stock 426 will pass.

I don’t know how much this varies with speed averages but the events I run typically go from 25 to 35 mph and I can count on 30 miles on a gallon. There is no sound test, which is good because all the YZ/WRs I see have aftermarket silencers and are way loud.

Hope this helps!

  • techman

Posted October 12, 2000 - 12:35 PM


The test is standardised by the MMIC and based on an SAE test spec. The sound is measured on the A scale, slow response with the meter about 20" away from the muffler tip. The engine rpm is at possibly 1/2 redline, or 1/2 max horsepower rpm, or calculated based on bore and stroke and hp, but there is a standard rpm specifically for your model of bike. They'll probably look it up in a chart they have for testing. A stock 426 is pretty loud and 102 dB sounds right. If they feel nice that day they may let you ride even though you're just over. If your muffler is clapped out because of lots of riding time (I believe they're packed with fiberglass) you'll likely exceed 102 dB.

An option I have pursued for neighbour friendly riding is to bolt on a WR426 pipe with the insert still installed. You'll pass 99 dB with flying colors. You may have to lean out your jetting a bit however. I don't find myself particulary "down on power" with this setup, as I wheelie and roost at will even with the WR pipe.

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