California Highway Patrol press release: 

On 06/22/2018, at 1035 hours, a 2013 Kawasaki ZG1400 motorcycle was being operated by Robert Bradley Knowles, 67 from SeaTac Washington, southbound SR-1 north of mile post marker 103.02 in an unincorporated area of Mendocino County. For reasons still under investigation, the Kawasaki traveled off the east road edge, down the tree and vegetation covered embankment, and collided with a tree. Knowles was transported by air ambulance to Mercy Medical Center in Redding, CA, where he was pronounced deceased at 1333 hours.

This collision remains under investigation by the California Highway Patrol- Garberville Office. 

The California Highway Patrol was assisted at the scene by Leggett Cal-Fire, Leggett Volunteer Fire Department, City Ambulance of Eureka, Westport Fire Department.