YS Engine YSF9135 Rocker Arm Screw F91AC  [YSF9135]

This YS Engine YSF9135 rocker arm screw is an RC-scale replacement fastener designed for the F91AC engine family. It serves as a direct fastener for the rocker arm area and is intended for routine maintenance and minor tuning work on small model engines.

Compatibility is focused on F91AC-design engines where the original part is specified. Installers should confirm thread size and engagement depth before reuse to avoid interference with valve movement. The part's role is purely mechanical: secure the rocker arm assembly and maintain correct valve motion geometry during setup and adjustments.

Installation notes: remove the valve cover and rocker assembly as required, verify alignment and torque to the engine maker's recommended range, and check valve clearance after tightening. For tuning, small changes to rocker mounting can affect valve timing and lift on model engines, so make incremental adjustments and re-check clearances.