Hatroi HA602 Replacement Nut Compatible with #643 #644 YS4C-63 and OS4C-70 RC Fittings  [HA602]

Scale RC fitting replacement nut

The Hatroi HA602 nut is supplied as an RC-scale replacement for the part numbers named in the title, including #643, #644, YS4C-63 and OS4C-70. It is intended to fasten model engine components and related fittings when the original nut is lost or worn.

Only the listed codes are supported, so confirm your model's part marking prior to purchase. Mechanically, this nut secures studs and fittings, maintains part alignment, and reduces vibration transfer that can affect idle and tuning stability in small engines.

Fitting is a straightforward workshop task: clean mating threads, engage the nut by hand to ensure correct thread alignment, then tighten to a firm but careful fit to avoid damaging threads. Reinspect after a brief operational test to confirm seating.

As a workshop spare, the HA602 is useful for quick swaps and preventative maintenance. Keeping identical fasteners on hand helps minimise downtime and keeps tuning consistent by avoiding misaligned hardware.