Yamaha SR400 front turn signal bulbs use a 1157 size while rear turn signal bulbs use a 1156 size. The replacement chart covers 2015 through 2018 model 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 Yamaha SR400 uses two distinct bulb types across its turn signal positions: the 1157 at the front and the 1156 at the rear, across the 2015-2018 model years.
The 1157 is a dual-filament bulb, meaning it carries two separate filaments within a single envelope, operating at 21W and 5W respectively on a 12V circuit.
The 1156 is a single-filament bulb, operating at 21W on a 12V circuit, with no secondary filament for a reduced-intensity function.
The 1157 uses a BAY15d bayonet base, which is an offset dual-contact base designed to prevent incorrect insertion by positioning its two pins at different heights.
The 1156 uses a BA15s bayonet base, a single-contact base with pins at equal heights, making it physically incompatible with the BAY15d socket used by the 1157.
Because the 1156 and 1157 share a similar physical profile but differ in base configuration and filament count, the two types are not interchangeable with each other.
Both the 1157 and 1156 are ANSI-standardized bulbs, meaning their specifications conform to a defined industry standard applicable in the United States and Canada.
Substituting a single-filament 1156 into a front turn signal socket designed for the dual-filament 1157 would result in an incomplete circuit connection due to the differing base contact configurations.