I'd advise a loop that crosses the central valley and runs down the foothills, crossing back east farther south.
If you're going to be up here in Marin County and want a nice loop, think about 1 out to Stinson Beach, on up to about Tomales, then cut inland and over 37 to head east on 80. If you've got a bit of time, I'd recommend a loop up over 121 to 128, which is a nice ride up through Napa and will show you some nice vineyards and spectacular views. From there, you can probably navigate a course over the valley, but 80 is expedient. From there, consider 49 south. You'll have an amazing ride over some spectacular roads and will go right by Yosemite. If 120 is open, you can cut through and over to Mono Lake and Lee Vining.
This route will keep you from having weather issues and will keep you from getting stuck. Traffic at Thanksgiving around Tahoe is horrendous, so I'd avoid, avoid, avoid.
You also do not want to get stuck in a snowstorm over 80 on a motorcycle. You'll be hard pressed to secure lodging if it all goes bad.
Fuck Cancer. Ride bikes. - dave + tina