Honda Motorcycle CB750C Custom Turn Signal Bulb Size
Honda Motorcycle CB750C Custom front turn signal bulbs measure 1034 in size, while rear turn signal bulbs measure P21W or 1073, with each bulb size specified for its corresponding location. The replacement chart covers 1981 to 1982 model years and contains vehicle production years alongside 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 CB750C Custom uses three distinct bulb types across its front and rear turn signals for the 1981-1982 model years: the 1034, the P21W, and the 1073.
The 1034 bulb follows the ANSI standard used in the US and Canada. It is a dual-filament bulb operating at 12V with a 21/5W output and uses a BAY15d bayonet base.
The BAY15d base of the 1034 is an offset-pin bayonet fitting, which physically prevents incorrect single-filament bulbs from being seated in its socket.
The 1034 is a variant of the widely used 1157 bulb type, sharing its dual-filament design and base configuration while differing in output characteristics.
The front turn signal position uses the 1034 bulb for both the 1981 and 1982 model years of the Honda Motorcycle CB750C Custom.
The rear turn signal position differs between model years. The 1982 model uses the P21W, while the 1981 model uses the 1073.
The P21W follows the ECE standard used in Europe and worldwide markets. It is a single-filament signalling bulb rated at 12V, 21W, and fitted with a BA15s bayonet base.
The 1073 is an ANSI-standard single-filament bulb with a BA15s bayonet base, rated at 12V and 13W. It is a lower wattage variant of the 1156 bulb type.
Although the P21W and the 1073 share the same BA15s bayonet base, their wattage ratings differ significantly at 21W and 13W respectively, making them non-interchangeable without affecting turn signal brightness and circuit load.
The dual-filament 1034 used at the front and the single-filament bulbs used at the rear indicate that the front turn signal housing on the CB750C Custom serves more than one lighting function within a shared socket.