Harvey Mushman & the others.

Hackman and Jody Weisel at Saddleback. Photo was posted to one of the Saddleback Facebook pages by Vic Armijo, so probably safe to say it's his photo.

Jimmy Johnson rode prior to the NASCAR gig

Townsend Bell (Indy Car / IMSA race commentator, IMSA Lexus Factory Driver and Brand Ambassador) and Jack Hawksworth (IMSA Lexus Factory Driver) are big motocross riders and Moto/SX enthusiasts.  Bell is a regular rider at Glen Helen and Pala.

https://sportscar365.com/features/commentary/bell-successful-first-avs-training-camp/

I was about to post about Ian Anderson of Jethro Tull but figured I'd better read through the whole thread first, glad I did. I remember reading an interview that Dirt Bike mag did with him back in the mid 70's; I believe Len Weed was the editor as it was after Super Hunky got pissed off and left. Ian was really into Ossa's at the time and also told a funny story about his farmer neighbor who would go out and chase his sheep around on a honda XL wearing slippers and a bathrobe! LoL

See him around town quite a bit. Good dude!

James Cameron has worn mx jerseys in several different interviews.

Yes he does. Saw him out at pala few years back 

Ian Anderson was featured in an episode of "Riding with Norman Reedus" several years back. Ian's daughter is married to Andrew Lincoln of "Walking Dead" fame. They all rode around Ian's English country estate on trials bikes near the middle of this clip....