Description
The factory Derbi machines of 1967 were the Derbi 50 GP model (internally known at the factory as the Derbi GP 50 Grand Prix or Derbi 50 "Ángel Nieto").

They were not yet formally called the "Red Bullet" (*Bala Roja*)—the name by which they would become popularly known years later (1969–1972) when Nieto dominated the World Championship—but they were genuine factory racing prototypes ("works bikes").

Features
- Engine: 49.8 cc single-cylinder, 2-stroke, air-cooled (featuring oversized, finned cylinder head and cylinder).
- Induction: Side rotary valve.
- Power: Between 14.5 and 15.5 HP at approximately 14,000–14,500 RPM.
- Gearbox: Special gearboxes developed by Paco Tombas, ranging from 8 to 12 speeds.
- Exhaust: High-mounted expansion chamber routing around the engine toward the tail section.
- Chassis: Ultra-lightweight tubular steel prototype with a custom factory swingarm.

The factory bikes were unique, hand-built prototypes created in Martorell (Barcelona) exclusively for the factory team, which included Ángel Nieto and Barry Smith. Unlike the privateer/customer bikes based on the *Derbi Carreras Cliente* models, the Derbi 50 GP was a dedicated official factory machine.

Credits
Irgam