Honda Motorcycle CB650SC Nighthawk Turn Signal Bulb Size
Honda Motorcycle CB650SC Nighthawk front turn signal bulbs use 1034 size while rear turn signal bulbs use P21W or 1073 size. The replacement chart covers 1982 to 1985 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 Honda Motorcycle CB650SC Nighthawk uses two distinct bulb types across its front and rear turn signals, spanning the 1982-1985 model years.
The 1034 bulb is the sole front turn signal fitment across all four model years, 1982-1985, on the CB650SC Nighthawk.
The 1034 is an ANSI-standard dual-filament bulb rated at 12V and 21/5W, fitted with a BAY15d bayonet base, and is classified as a variant of the widely used 1157.
A dual-filament design means the 1034 serves two lighting functions from a single bulb, with the higher 21W filament typically handling the turn signal function and the lower 5W filament handling a secondary function such as running light duty.
The rear turn signal on the CB650SC Nighthawk does not use a single bulb type across all model years, as the 1984 model year specifies the 1073 while 1982, 1983, and 1985 specify the P21W.
The 1073 and P21W are not interchangeable despite sharing the same BA15s bayonet base, because they originate from different standards and carry different wattage ratings, 13W for the 1073 and 21W for the P21W.
The P21W is an ECE-standard single-filament bulb rated at 12V and 21W, and its BA15s bayonet base is a single-contact fitting, distinguishing it from the dual-contact BAY15d base of the 1034 used at the front.
The 1073 is an ANSI-standard single-filament bulb rated at 12V and 13W, described as a lower wattage variant of the 1156, and shares the BA15s bayonet base with the P21W.
Because the front turn signal uses a BAY15d base and the rear uses a BA15s base, the front and rear bulbs on the CB650SC Nighthawk are physically non-interchangeable regardless of model year.
The 1034 and P21W represent a cross-standard fitment on the CB650SC Nighthawk, with the ANSI-standard 1034 at the front and the ECE-standard P21W at the rear for most model years.