Honda Motorcycle FT500 Ascot Turn Signal Bulb Size
Honda Motorcycle FT500 Ascot front and rear turn signal bulbs use P21W and 1073 bulb sizes respectively. The replacement chart covers 1982 to 1983 model 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 P21W is an ECE-standard single-filament bulb rated at 12V and 21W, fitted with a BA15s bayonet base. It is used in the front turn signals of the Honda Motorcycle FT500 Ascot for both 1982 and 1983, as well as the rear turn signal for 1982.
The 1073 is an ANSI-standard single-filament bulb rated at 12V and 13W, also using a BA15s bayonet base. It appears in the rear turn signal position for the 1983 model year only.
The BA15s bayonet base is shared between the P21W and the 1073, meaning both bulbs use the same physical mounting interface despite originating from different regional standards.
Although the P21W and 1073 share the same BA15s base, their wattage ratings differ significantly. The P21W draws 21W while the 1073 draws 13W, which means the two bulbs are not electrically interchangeable without potential effects on turn signal flash rate or circuit load.
The rear turn signal of the FT500 Ascot changed bulb specifications between model years, with the 1982 rear position using the P21W and the 1983 rear position using the lower-wattage 1073.
The 1073 is classified as a lower-wattage variant of the 1156 bulb. The 1156 is a widely used ANSI single-filament bulb also rated at 12V but at a higher 26.88W output, so the 1073 is not a direct substitute for it.
The front turn signal position remained consistent across both documented model years, with the P21W specified for 1982-1983.