Authorities have identified a man who died Saturday night after a solo motorcycle crash on Highway 121 near Sonoma Raceway. 40-year-old Kevin Miller, a Santa Rosa resident, was riding a motorcycle north on the highway at an “unsafe” speed when he lost control on a turn just north of Highway 37, went across the lanes and crashed into a concrete bridge wall and guardrail. The CHP responded at about 8 p.m. and saw Miller dead on scene. He was identified Monday by the Sonoma County Sheriff’s Office. The agency is still looking into the crash.