>>1581661You took the time to see whether the locations I suggested offered motorcycle trails, but you didn't bother to offer up any locations where he could...
As far as I am aware, there are no places in Northern California that allow motorcycles off-road. The OP's request is not California legal. Also, any location where you could drive your vehicle (motorcycle) all the way up to the lake is not going to be secluded, its going to be filled with all the other lazy tourists who also drove their vehicle all the way up to the lake.
Theoretically you could illegally drive your motorcycle down a dirt path to one of the lakes I have listed above, but if a park ranger sees you, they are going to slap you with a $300+ ticket.
Rather than trying to drive your motorcycle to the lake itself, I would recommend simply parking the motorcycle at the trailhead and hiking a dirt path to a secluded lake. My top recommendation is 20 Lakes Basin, has lots and lots of little and big lakes and the farther in you hike, the more secluded it gets.
As far as places in the High Sierra/Sierra-Nevadas with lakes that you can take a regular dirt bike.
-Lake Tahoe
-Bear Valley
-Lake Almanor near Chester
-Whiskeytown-Shasta-Trinity National Recreation Area
-Plumas Eureka State Park
Lake Tahoe seems to be the OP's best bet, it's the only one that allows motorized bikes to go down. Just beware that a street-legal motorcycle is not considered a motorized dirt bike.
