I just looked at the body of the new noise limitation law which restricts most modern bikes to 96db on the CA OHV website. The law says measured at 20"; however, there is no measuring criteria other than SAE Standard J-1287. Anyone out there have this criteria or measuring standard? It's available from SAE for a cost of $47.00, but thought I'd ask before spending my hard earned cash.

I have a sound level meter, and would like to know just how the actual test is performed so when the rangers says my bike doesn't cut it, I'll be prepared!

Here is what the Rangers do do at Hollister Hills: They have a 20" piece of string attached to the "microphone" on their sound tester. The hold the other end at the end of your silence and move away from the bike so the string comes of the silencer at a 45 degree angle and level to the ground. Then another Ranger holds the throttle to keep the RPM at the test level (different for different bikes) using a vibratach on the radiator shroud to monitor RPMs. There is some debate as to what RPM the YZF/WRF are to be measured at. I think the regulation says half the rev limit which would be 6750 but I am pretty sure thy tested my WRF at 4500 rpm. You also have to have the sound tester in dbA mode, whatever that means.

That's the same SAE standard that is used in Michigan, and Rick describes it pretty well. The RPM level chosen is out of some little pocket sized book, and as of last year I don't think the 250F's were in it. So they chose a random Yamaha and went for it with the choice being between 4k - 5k RPM's. I think most of the vibratach's are around 4k RPM's.
dB(A) and dB© are the two sound pressure level (SPL) weighting curves. dB© mimics the human ear and gives a MUCH higher reading. We'll take dB(A) anyday.

Along with dbA (i.e. weighing 'A'), I think you're supposed to also set the sound sensitivity to average (or low) I forget the correct term, but this makes the meter averages out the sound vs. having spikes everywhere if you use the other setting (high?) - stand behind your exhaust pipe at 45 degrees to the right, 20" back, parallel to the ground, point the meter at the exhaust pipe and run the bike at a steady RPM (supposed to be 1/2 the max RPM but it's actually different in real life as you can see from the reports).

Thanks for the clarifications on procedure. I have kind of done what has been suggested, and no way does my bike come close to the 96db level. I have a FMF Ti4 muffler and midpipe. I am trying to fabricate a light weight tip to put on the end to help quiet the Ti4 down, no small task!

I think you mean "slow" response (as opposed to "fast" response.) I have always measured sound levels (on any type of noise) using the slow response setting.