Honda Motorcycle VTX1800R front and rear turn signal bulbs use a 12496 PY21W bulb size. The replacement chart covers 2002 to 2008 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 two bulb types specified across all model years of the Honda Motorcycle VTX1800R turn signals are the 12496 and the PY21W, both rated at 12 volts.
The 12496 is a halogen bulb designated by a Philips/Osram part number, intended for specialty automotive applications rather than general-purpose use.
The PY21W follows the ECE (Economic Commission for Europe) standard, a regulatory framework used in Europe and numerous other markets worldwide. It is a single-filament amber bulb producing 21 watts of power.
The PY21W uses a BAU15s bayonet base, an offset-pin bayonet mount that prevents accidental installation of non-amber bulbs into amber-designated sockets. This base is not interchangeable with the standard BA15s bayonet base.
For the front turn signal on the Honda Motorcycle VTX1800R, the 2002-2004 model years use the PY21W, while the 2006-2008 model years use the 12496.
The rear turn signal fitment does not follow a uniform pattern across model years. The 2002 rear uses the 12496, the 2003 rear uses the PY21W, the 2004 rear returns to the 12496, the 2005 rear uses the PY21W, and the 2006-2008 rear uses the 12496.
The 2005 model year is the only year in which both the front and rear turn signals share the same bulb type, the PY21W, across both positions simultaneously.
Because the 12496 and PY21W differ in base type and origin standard, they are not interchangeable, and substituting one for the other in a given socket is not supported by these specifications.