Honda Motorcycle GB500 front turn signal bulbs use 1034 size while rear turn signal bulbs use P21W size. The replacement chart covers 1989 to 1990 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 Honda Motorcycle GB500 uses two distinct bulb types across its turn signal positions: the 1034 at the front and the P21W at the rear, both for the 1989-1990 model years.
The 1034 is an ANSI-standard bulb used in the United States and Canada. It operates at 12V with a dual-filament output rated at 21/5W and uses a BAY15d bayonet base.
The dual-filament design of the 1034 means it carries two separate circuits within a single bulb, typically serving both a brighter and a dimmer function depending on the application.
The 1034 is a variant of the 1157, a widely used automotive bulb. Despite this relationship, the two are not always interchangeable, as minor differences in base pin spacing or filament positioning can affect fitment.
The P21W is an ECE-standard bulb recognized across European and international markets. It operates at 12V with a single-filament output rated at 21W and uses a BA15s bayonet base.
Because the 1034 uses a BAY15d base and the P21W uses a BA15s base, the two bulb types are not interchangeable. The BAY15d base has offset pins to prevent incorrect installation, while the BA15s base has a single contact and symmetrical pins.
The front and rear turn signals on the Honda Motorcycle GB500 follow different international standards, with the front conforming to ANSI specifications and the rear conforming to ECE specifications.
Both the 1034 and P21W share a 12V operating voltage, making them compatible with the same electrical system, though their wattage and filament configurations differ.