Honda Motorcycle CB900C Custom headlight bulbs use 9003 size for both high and low beam functions. The replacement chart covers 1980 to 1982 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 bulb is an ANSI-standard halogen type recognized in the United States and Canada, operating at 12 volts with a dual-filament design rated at 60 watts on the high beam filament and 55 watts on the low beam filament.
The P43t base is a bayonet-style mount with a 43mm flange, which physically determines socket compatibility and is a critical factor in fitment.
Because the 9003 bulb contains two filaments within a single housing, it serves both high and low beam functions from one unit, which is reflected in the Honda Motorcycle CB900C Custom specifications listing the same bulb size for both sub-parts.
The CB900C Custom used the 9003 bulb across all three model years covered in the specifications, spanning 1980-1982, for both high and low beam headlight positions.
The 9003 designation is the ANSI equivalent of the international HB2 standard; however, fitment interchangeability between 9003 and visually similar single-filament types such as 9005 or 9006 is not supported, as those lack the dual-filament configuration and use different base designs.
The wattage split of 60W/55W in a dual-filament halogen bulb is a standard characteristic of the H4/9003 family, where the higher wattage filament is positioned to produce the wider, farther-reaching high beam pattern.