An 18-year-old Maui man suffered life-threatening injuries, when his motorcycle was struck by a sedan Friday at 7:15 p.m. It happened near the intersection of Piilani Highway and Kaonoulu Street in Kihei.  The sedan, driven by a 48-year-old Kihei man was traveling north on Piilani Highway and made a left turn onto Kaonoulu Street into the path of the motorcycle traveling south on the highway. The motorcycle collided with the passenger side of the sedan. The motorcyclist was wearing a helmet, police said.