Holders of a class B driver's license held for more than... may ride a motorcycle of up to 125 cc within the national territory.

Correct answer: 3 years.

If you have held a category B driver's license for more than three years, you may ride motorcycles covered by a category A1 license in Spain, with up to 125 cm³ of engine displacement, 11 kW of power, and a power-to-weight ratio of 0.1 kW/kg. If you have held your B license for one or two years, you are not allowed to do this yet. This authorization is not valid outside Spain.

Real Decreto 818/2009, de 8 de mayo, por el que se aprueba el Reglamento General de Conductores