BMW Motorcycle K100LT high beam and low beam headlight bulbs both utilize a 9003 size. The replacement chart covers 1987 to 1992 production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The BMW Motorcycle K100LT uses the 9003 bulb for both high beam and low beam headlight positions across the 1987-1992 model years.
The 9003 is a dual-filament halogen bulb, meaning a single bulb unit contains two separate filaments to serve both high and low beam functions within one housing.
The 9003 operates at 12 volts 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 is designated as an ANSI standard bulb applicable in the United States and Canada, and it is functionally equivalent to the H4 bulb used in international markets, though the two designations reflect different regional certification standards.
Because the 9003 serves both beam positions on the K100LT, a single replacement bulb type addresses the entire headlight assembly rather than requiring separate bulbs for each function.