90206-PM3-004 Tappet Adj Nut - Overview. The 90206-PM3-004 Tappet Adj Nut is a critical component within Honda marine engine systems. It serves in the valve train system, specifically to secure and adjust the valve tappet, which is essential for accurate valve timing and optimal engine operation. This nut ensures seamless integration with existing parts, maintaining optimal performance and durability.. Key Features. Precision machined adjusting nut for valve tappet in the Honda marine engines..