Most off road racing questions should be directed to the local club that is hosting the event. The AMA is basicly a sanctioning body that is made up of vollunteers out here that put the time in that makes things happen.
Tech insp for off road usually entails having a FS Legal spark arrestor and proper number/color combination displayed on bike.
Unless you are a Pro-A- Rider you will be issued a number at the event upon sign up. There is no universal way of doing things.
Check out some of the web pages for off road clubs and they will have plenty of info for you, and ask questions at local shops.
Folks are more than happy to see new faces off road, just show up with out an attitude and folks will be more than willing to help.
http://www.moto-directory.com/clubs/off-road.htm
This site has some NW clubs aand they will have more links.
Have Fun----AMA Field Rep #869
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Ken James
XR400 Honda
If you Don't --Who will ?