These are recommendations from a 1994 copy of Bed, Breakfast and Bike.I haven't ridden any of them.
Bucks Lake Loop 33.1 miles If you do it counterclokwise you climb a 15% grade which done clockwise is a "hair-raising descent" Sounds like fun!
Scenic Feather River Highway 63.8 miles, "relatively rolling terrain and scenery typical of the region" The map shows it as highway 70/89 to Blairsden, turn tight on, Blairsden Road. You can turn around at this point or continue on to Mohawk Valley Road which should take you to the Plumas-Eureka state park and then loop back out to the highway. Doing this loop involves some "serious climbing."
Have fun!
Veronica