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

The YS Engine YSS9117 back plate O-ring is a service replacement made to interface with 91SR back plate assemblies on RC engines. Its role is to seal the joint between the back plate and engine housing to reduce fuel and oil leakage during use.

Fit and compatibility: designed to suit the back plate interface of 91SR engines, this O-ring offers a direct sealing solution without altering plate geometry. Inspect the mating surfaces and groove for damage prior to fitting to ensure a secure seal.

Installation notes: remove the existing O-ring with care to avoid scratching the bore, clean all mating areas, and set the new ring flat in its groove. A small amount of compatible lubricant can help the ring seat evenly and prevent twisting. Conduct a static leak check before returning the engine to service.

Replacement guidance: while not an upgrade part, a fresh O-ring is important to maintain consistent engine operation. Swap the seal during routine engine servicing if the ring shows wear, deformation, or you detect seepage.