HPI Roto Start System (For Nitro Star K Series Engine w/Pullstart). New from HPI is the Roto Start system for the HPI K Series engines, including the extremely powerful K4.6! The HPI Roto Start system replaces the standard pullstarter with a durable metal gear backplate and a handheld shaft driven starter, making starting engine as simple as pressing a button. Available in two versions, one with the complete Roto Start handheld starter plus the engine backplate, and another with just the engine backplate.