Sound Vs. Ignition

Just got May’s Dirt Rider. In the KTM250SFX test they talk about how loud the bike is (about 106dB). They blame this mostly on the ignition box. They state, “The stock ignition fails to recognize high RPM with no load situation, in doing so it doesn’t advance the timing to quiet the bike down. That’s how most bikes are passing the sound test.”

Is this new? Have the Japanese bikes been doing this for long? Does anybody know if, say a 2001 YZ250F has this ignition? I noticed that the bike has a gear position sensor. If I fail the sound test with stock exhaust at the first NETRA event is fiddling with ignition better than trying to repack the muffler? Is NETRA’s limit 99dB?

Dirt Rider goes on to say they installed a Vortex ignition on the 250SFX and it passed a 99 dB test with a FMF muffler. I know there’s a lot of question marks in this post but maybe it will start some discussions. Thanks.

It is a built in cheating method to make the bike pass the sound test. It comes from the factory or it doesn't. I think this is a newer 2005 or later addition.

Other cheating that goes on. WR's come with a block that only lets them go to half throttle. So they get tested at 40% of half throttle. Much easier to pass the sound test. Yamaha knows people will change the throttle stop. Now we have louder bikes.

It's cheaper just to repack your muffler.

Keep riding areas open. :thumbsup:

Urbanexr you are right.

Noise testing here in Australia is done in neutral stationary at a RPM, similar to the FIM test and a Vortex will reduce noise. We use them on pro bikes partially for that and partly for the performance mapping to suit a motor.

Is this why when you rev a 250f on the stand its not very loud if you twist the throttle slowly, but if you crack it open it is considerably louder?

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