Since 1985, the 34091-85 inner bearing race has been employed in Big Twins. The inner primary bearing rests on this race, which is designed to press-fit onto the transmission mainshaft. This setup functions well for stock engines. However, engines with 100 HP or more can cause the race to shift on the mainshaft. If it moves inboard, it can damage the maindrive gear seal, leading to a transmission oil leak. If it shifts outboard, it results in a primary oil leak. Our high torque bearing kit resolves this issue, including a precision honed bearing and seal.