There is a hiking trail that crosses over the route at the very beginning that is off-limits to bikes, and it is a bit confusing at the beginning. Just remember that the Marlette Creek Trail
starts out on a steep fireroad climb and NOT on singletrack and you are good to go...
This trail starts on a steep climb on a fire road right below the kiosk at the top of the North Canyon Road
climb from Spooner Lake to Marlette Lake. It climbs for a very short 0.4 miles; then as you crest the climb, the singletrack starts on your right (look for signage).
The trail is narrow, fast, and very flowy with berms, kickers, and big granite rollers. It tunnels and slaloms through ponderosa, jeffrey, and lodgepoles pines at a blurring pace. Toward the bottom, it opens up a bit, and the trail gets loose and sandy especially during the summer months. At the bottom, you dump out at Chimney Beach Parking area where you can continue across the road and down to the shore of Lake Tahoe for a dip in the Big Blue.
From Chimney Beach, the only way back is using the road (super sketchy) or climbing back up Marlette Creek trail (which is brutal). So your best bet is to set up a shuttle or, better yet, arrange a shuttle with flumetrailbikes.com. They can scoop you up for a reasonable rate so you don't have to worry about the return trip.