Order code: OLFSS006. Lexmoto: Chieftain 125 TD125T-15, FMR 125 EFI WY125T-74R-E4, FMX 125 EFI WY125T-108-E4, Vienna 125 EFI WY125T-121-E4, Vienna 125 WY125T-121. Mitt: Mitt 125 GTS MITT125GTS. The oil filter retaining spring on a motorcycle is a component that holds the oil filter securely in place within the engine.