BMW Motorcycle K100RS FL headlight bulbs use 9003 size for both high and low beam functions. The replacement chart covers 1991 to 1992 production years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 9003 is a dual-filament halogen bulb operating at 12 volts, with a high beam output of 60 watts and a low beam output of 55 watts. It uses a P43t base, which is a standardized bayonet-style fitting common across many halogen headlight applications.
The 9003 designation follows the ANSI standard used in the United States and Canada. This standard defines the bulb's electrical and physical characteristics, making it distinct from the European H4 bulb, which shares a similar dual-filament halogen design but uses a different base configuration and is not directly interchangeable.
The BMW Motorcycle K100RS FL uses the 9003 bulb for both the high beam and low beam headlight positions across the 1991-1992 model years. A single bulb type serving both functions is consistent with the dual-filament nature of the 9003, where each filament corresponds to one beam mode.
Because the high beam and low beam positions share the same 9003 specification, only one bulb type is required to service the entire headlight assembly on the K100RS FL.
The P43t base is a keyed fitting, meaning the bulb is designed to seat in only one orientation within the headlight housing. This prevents incorrect filament alignment, which would otherwise cause the high and low beam filaments to project light in unintended directions.