HA237 Copper Gasket by Hatroi (fits #643 #644 YS4C-63~70 OS4C-70~81)  [HA237]

Replacement copper washer for glow engine sealing

This Hatroi HA237 copper gasket is supplied as a direct-style spare sealing washer for the engine codes quoted in the title. It is intended to re-establish a leak-free joint between cylinder head and block when performing normal maintenance or rebuild work.

Functionally the gasket fills microscopic irregularities at the head-to-block interface to help sustain compression and limit external leakage that can follow disassembly or long service intervals. Always confirm the engine model codes in the listing before purchase to ensure correct fitment.

Fitment tips: remove any old gasket traces, wipe both faces clean, seat the copper gasket flat and centred, then reassemble and tighten progressively in the pattern your engine maker specifies. Do not over-torque, perform a cautious run-in and then recheck fastener tensions once temperature stabilizes.

For troubleshooting low compression, replacing an aged or distorted copper gasket like the HA237 is a sensible diagnostic step to determine whether sealing is the issue rather than internal component wear.