BMW Motorcycle K100RS headlight bulbs utilize a 9003 size for both high beam and low beam functions. The replacement chart covers vehicle production spanning 1983 to 1989.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The BMW Motorcycle K100RS uses the 9003 bulb size across both the high beam and low beam headlight positions for the 1983-1989 model years.
The 9003 is a dual-filament halogen bulb, meaning a single unit contains two separate filaments to serve both high and low beam functions within one housing.
Despite the dual-filament design of the 9003, the K100RS specifications list it separately for both the high beam and low beam positions, indicating the motorcycle uses dedicated housings for each function rather than a single combined unit.
The 9003 operates on a 12-volt electrical system and carries a wattage rating of 60W on the high beam filament and 55W on the low beam filament.
The 9003 uses a P43t base, which is a bayonet-style mount with a 43mm collar, and this base type determines physical fitment into the headlight housing.
The 9003 designation follows the ANSI standard applicable in the United States and Canada. The same bulb is sold under the designation H4 in international markets, though labeling differences may affect packaging and retail availability.
Because the P43t base is a standardized mount, bulbs from different manufacturers carrying the 9003 designation are generally interchangeable at the socket level, provided they match the 12V and 60W/55W ratings.
Substituting a single-filament bulb in place of the dual-filament 9003 would be incompatible with the socket and wiring configuration of the K100RS headlight positions.