13420-RAD-010 RR Balancer Shaft - Overview. The 13420-RAD-010 RR Balancer Shaft is a crucial OEM component for Honda marine engine systems. Its primary role is to balance the rotational forces inside the engine, significantly reducing vibrations that can impair engine performance and cause wear over time. This part is designed to fit seamlessly within the rear section of Honda engines, providing reliable and long-lasting operation.. Key Features. Genuine Honda OEM rear balancer shaft designed to