Carnegie to the South, or cow mountain near Ukiah to the North for Dirt Bikes is your best bet.
Nothing motorized
Montain bikes/bicycles yes. Motorcycles arw not allowed in any regional parks including Black Diamond. Carnegie svra would be the closest place other than tracks
AsJackie said, no motorized vehicles. Historic site and wildlife preserve.
I doubt it. I've been there at least six times and I've never seen bicycles or motorcycles on the trails. Nor any signs for a place to do that.
NO, motorized bikes and/or vehicles
As far as i know they are not since its a historical area. You should be able to find a number to the Ranger Station or the number for mine tours & they should be able to answer your question
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