Yamaha Radiator Pipe Joint YF1-89617-31-70. Overview. The Yamaha YF1-89617-31-70 Radiator Pipe Joint is a genuine original equipment manufacturer component designed to connect sections of the cooling system and allow coolant to flow efficiently between radiator pipes. This joint helps maintain proper coolant circulation, ensuring the engine remains within its optimal operating temperature range.. Reliable connections within the cooling system are essential for preventing leaks and maintaining st