My lovely wife taught Public Speaking at several colleges and online for about 17 years. You have my sympathy. :rotfl:
Hope these links are helpful. Might not be exactly what you're looking for.
From the North Carolina Hare Scramble Association. Plenty of race starts, crashes, mud holes and other stuff. Use the "web videos" button. Might find something useful:
NCHSA(link)
Nick Hamill's Racing Website. Under the "videos" section you'll find mostly helmet cam vids of enduros and hare scrambles, but there are some mx vids as well.
Nick Hamill Racing (link)
You'll also find some AHRMA race video (including fairly recent Brad Lackey- if you know who he is) under "Latest MX Video" at:
Evo-Sports, Inc.(link)
Hope that's helpful and g/l