Sound Test Report

When riding at Stoneyford in Northern Calif. this weekend. Got sound tested by the rangers. It's good to the testing and letting everyone know what they test at and those that fail (my nephews 96 CR250) what kind of pipe will past.

01-WR426, stock header,stock jetting,grey wire mod,airbox lid off,two rides on repack (silent sport packing),WB E-Series 8 disc and quit core (did not notice any power loss)bike warmed up and rider sitting on bike,RPM 4500.

Tested at 98.9 :)

Ride Safe, Ride Often and Have Fun :D

do you have an TACH on your bike. How do you know you are at 4500 RPM.

The Rangers have Briggs & Straten Tach. It's a small round meter with a wire that sticks out, they sit it on your rear fender and read the sound meter when it hits 4500rpm, all bikes get tested at different RPM'S. The rangers have a book that tells what bikes should be tested at. These are the same tach's they use for testing on Lawnmowers and gas powered buffers. I hope this helps. If you do a search I know this was talked about in great length on the KTM side awhile back. RetSenior has bought his own sound testing equipment and posted on the KTM side.

yea but where is it connected or does it go off of vibration. How does it get connected

It does not get connected any where, it just sits on your rear fender, the wire that comes out is about 3inches long and is more like an antenna wire. There is a more detailed post somewhere on the KTM side that explains it better then my lame technechol mind. :)

It probably reads the electric discharges from the coil.

My guess is that the 'adjustment' changes the length of the wire and thus changes it's natural frequency. Rev the bike until the wire goes ape **** and viola - your there.


downside of this type of testing is that the engine is under little load.

A 50' drive-by at WFO is a better measure of overall sound output.

It's a standardized test that we are all going to have to live with. I'd love to see a ranger try and conduct a 50 ft drive by test at an OHV staging area........


so if it is not connected then how does it measure the RPM's

To the top :)

What would be the "failing" DB level? Do you know how much the quite core insert reduces in DB's? I hear the insert causes major power haven't experienced this?


02'YZ426, e-series (8 discs), e-line skidplate, pro-tapers, fuel screw mod.

The tool they use for determining the bikes RPM is called a vibratach and is incredibly accurate if used correctly I have used this tool many times when I was in the marine repair industry. There are a few different styles the one I have is like a pen you place one end on the engine some place and slowly slide the wire out till it moves the most then read the RPM off the side. We would use it to determine the correct prop pitch or any time knowing the RPM was desired. You can find one here.

JT1 I think the sound level should be 99.9dbs They are talking of lowering it to 96dbs. From what I have heard from other Yamaha riders is the E-Series with 12 disc is 104dbs. I personally could not tell of any power loss for heavy ass :)

There was a good post awhile back on the KTM side that explained alot more.

The sound issue will probably never be solved. Its 99 now but when most get down to that level then they will want us to go to 96, then 93, and on and on until we ride mopeds. I am currently modifying my XL1000 (garbage disposal) to fit in my xr600 frame as the sound level is only 60db and I figuire that will make THEM happy, now if I can only find a way to get another 1000ft of extension cord connected to the bike????????????

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