I agree with Rod. A great ride. I stayed a couple of nights in Winthrop. Departed Winthrop about 9:00 AM heading west. Still chilly in late July at that time of morning. Riding west with sun behind me worked well for pictures. Went as far as Marblemont. Had lunch and started back. The return trip was all about the road. By midday tourist traffic was picking up but not a problem. Keep an eye out for an occasional fallen rock. Scenery is spectacular. Couldnt get the grin off of my face. WATCH FOR DEER as you drop out of the mountains and cross the meadows returning to Winthrop. Particularly in late PM / early evening.
If you are going to return to the Seattle area consider a loop down 97 to 2 west. Overnight in Leavenworth [A Bavarian Village theme town]. Then return to Seattle / Everett on Rt 2. You wont be disapointed.
The North Cascades Highway is the premier motorcycle road in Washington State. This one has sections of sweepers, esses and some tight corners. Combine that with beautiful scenery through the North Cascades National Park and great road surface and you won't be disappointed. The best part of this highway is about 80 miles long with its eastern terminus near Mazama, Washington, and ends in the west at Rockport. This is the northernmost pass across the Cascade Mountain Range in the United States. The old-west-themed town of Winthrop, Washington is just 10 miles west of Mazama and makes a good overnight stop.