Hatroi HA602 Nut for RC Engine Fittings #643 #644 YS4C-63 OS4C-70  [HA602]

Fastening nut for engine fittings

The Hatroi HA602 nut is provided as a replacement part for the listed codes in the product name: #643, #644, YS4C-63 and OS4C-70. It is intended to secure model engine fittings where the original nut is lost, worn, or being changed during routine service.

Fitment is confined to the specified part numbers, so check your model's marking before ordering. Functionally the nut secures mating studs and components, maintains correct alignment, and helps control vibration transfer that can influence idle and tuning stability on small RC power units.

Fitting is direct and workshop-friendly: clean mating threads, begin by hand threading to confirm correct engagement, then tighten to a snug setting without over-torquing to protect threads. After initial test running, recheck seating and tighten if necessary.

Use the HA602 as a basic service spare: swapping worn fasteners prevents misalignment and inconsistent behaviour, and carrying spare nuts reduces time lost to field repairs.