90017-ZVL-701 Tappet Adj Screw - Overview. The 90017-ZVL-701 Tappet Adj Screw is a crucial component used in Honda marine engine systems, specifically designed to adjust the valve tappet clearance. This precision screw plays a vital role in maintaining optimal valve operation, which is essential for sustaining engine performance, efficiency, and longevity. By ensuring accurate clearance adjustment, it supports proper mechanical timing and valve function, preventing engine wear and maximizing rel