O.S. Engine OS25881220 - Rotor Guide Spacer (40L) 55HZ for R/C engines  [OS25881220]

Role, fitment and maintenance notes

This rotor guide washer is produced as a precision spacer for R/C-scale engine rotor stacks. It preserves rotor positioning when you strip and rebuild the unit, helping to keep alignment consistent during routine maintenance or tuning of nitro R/C engines.

Model technicians and constructors fit the washer between rotor parts to control end-play and maintain concentric rotation. Its stabilising role helps cut down on repeated adjustment when balancing the rotor or setting timing.

Installation notes: undertake head or rotor housing removal in line with the engine service manual, insert the washer at the appropriate point in the rotor stack, and check that clearances meet the engine's service criteria. Only use thread-lock or apply torque where the manual specifies; the washer is a passive spacer and does not replace bearings or seals.

Maintenance tip: whenever you alter carburetion, ignition timing, or porting, re-confirm rotor alignment. Slight shifts in stack height can alter balance and running consistency, so always measure and verify rather than assuming fit remains correct.