YS Engine YSS9117 Back Plate O-Ring for 91SR Series  [YSS9117]

This YS Engine YSS9117 back plate O-ring is an RC-scale replacement seal engineered to mate with 91SR-series back plate assemblies. It helps prevent fuel and oil leaks where the back plate meets the engine housing, preserving reliable operation during service and running.

Fit and compatibility: the seal is sized to match the back plate interface used on 91SR engines, offering a direct replacement without altering the back plate geometry. Confirm the groove and bore are intact before installation to ensure proper fit.

Installation notes: remove the old ring carefully to avoid nicking the back plate bore, clean mating surfaces thoroughly, and seat the O-ring evenly in its groove. A light, compatible lubricant can ease installation and prevent twisting. After assembly, perform a static leak check before returning the model to regular use.

Maintenance role: though not a tuning item, a serviceable O-ring supports consistent engine performance by maintaining correct sealing under normal operation. Replace as part of routine servicing when the ring shows flattening, cuts, or any loss of sealing performance.