Mower displays E21 and stops; the message may indicate a front wheel or caster error.

Safety: Switch OFF the mower and wait for blades to stop before lifting the front end.

• Inspect caster wheel: Lift the front of the mower and spin the caster wheel by hand. Remove any wrapped grass, string, or debris.
• Check bearing play: Wiggle the caster wheel side to side. Excessive play or grinding noise indicates a worn bearing.
• Clean mounting fork: Remove packed dirt from the caster fork and pivot so the wheel can swivel freely.
• Test operation: After cleaning, run the mower on a flat surface and observe if E21 reoccurs.

If the wheel remains stiff or the error persists, replace the Yarbo Front Caster Wheel Assembly.