Yw50 Service Manual _top_ -

10W-40 motorcycle oil or 15W-40 diesel oil. Car oil lacks ZDDP (zinc) for flat-tappet camshafts. Use JASO MA/MA2 rated oil only.

Scooters are sensitive to fluid levels.

"Always support the scooter on the center stand + jack. The YW50 has a high-tension CDI – disconnect battery before touching ignition wires." yw50 service manual