UMS 5-55cc O-RING (INLET PIPE) ( X 10 QTY / Pack)

This is the o-ring (inlet pipe) for the UMS 5-55cc engine, the five-cylinder 55cc four-stroke radial from UMS.

The part itself is the O-ring sealing the inlet pipe joint.

Why it is replaced: a hardened O-ring at this joint is a classic source of a lean-running cylinder on a radial. Supplied as a pack of 10, which is how these small parts are normally bought — you rarely need just one.

Fitting note: Renew on every disturbance and check the groove for damage.