Answer to (some) midrange patchiness

I made a post on Derek's thread reference finding out more and letting you all know.

So here goes.

Apprently these bikes are wire to conform to an ISDE rule regarding decibel requirements. It's called a sound check and apparently at a certain rpm, in order to race, your bike cannot exceed a certain level. They have a "built in sound check", electronically. When you reach the rmp mandated (beats me what it is), the CDI does the sound check, fulfilling the mandate. For those of you not racing at the time and driving on the road, this is the cause of the patchiness mentioned by many of you in Derek's post.

There's a grey wire coming from the CDI unit.

If you snip it the sound check is disabled and eliminates this problem and will not affect anything else on the bike.

Unfortunately, my bike has more dreadful ills (fried source coil #2) and I haven't been able to notice the difference just yet.

Hope this helps. Cheers

This on all 2001 models ?

sounds intresting....

thanks, I'll look into it


What I was told was all 2001 model WRs. Additionally, I've been told most tech's are unaware it even exists.

what they are saying is that the ignition timing is retarded for-say-a thousand revs. this quietens the bike down.

the manufacturer &/or rider must supply the bore & stroke of the engine. it used to be so that people were declaring the CC. nowadays it's so the decibal man can check your bike.

the longer the stroke the lower you have to hold the revs. if you watch "on any sunday" they had to go by the DB man's little tent at a certain speed/revs!!!

there are one or two things you can do to help get through the DB check.

1) do it whilst on grass

2) shove something inside the pipe

3) hold the bike continually just under the revs they ask for citing a poorly jetted bike

4) sit on the silencer or place your boot on it


Is this the same as the little gizmo just under the gear lever that limits decibels when in 'neutral' but doesn't affect anything when a gear is selected?

I know one of the aftermarket Co's does a cover for it as many MX guys would remove it.


I fail to see the point of this sound check thing....

Does it actually make any difference to the noise level??

I can't imagine it making a significant change.

Are you blokes sure this is the source of the patchyness problem?



I'll be getting my bike back next week with a new base assembly. The Yamawrench said he already snipped the grey wire. I'll have first hand info after that. He's a pretty smart cookie (would I trust anyone but?). After reading the posts about the problems and the comments that theres no loss of power with a little twist o'throttle, I'm betting this is what people are experiencing.

I'll keep you posted if your hesitant to break out the wire cutters. :)

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