.
It's not atv's, but if your looking for something to do tomorrow and like the old or new 2 stroke MX bikes, there is a "2 Stroke World Championship" race at Glen Helen. Wiseco, Fasthouse and ARX (American Retrocross) are the sponsors. There may be a few old school riders there like Scott Burnwurth, Rex Staten, and Brad Lackey etc. It will be mostly newer 2 strokes but there should be several vintage bikes there as well. This is one of the bigger MX events of the year in So Cal.
If you have any questions just let me know.
http://glenhelen.com/event/2-stroke-mx-championships/
This is a short video from the event last year.
https://www.youtube.com/watch?v=bwCmFfcls5U
.