OS Speed 21XZ-B Spec II Engine

Factory tuned for maximum performance!

For years top drivers worldwide have equipped their rides with O.S. Speed engines because they deliver race-winning performance — and the 21XZ-B Speed Spec II is engineered to take that performance to the next level! Special modifications make this power plant even leaner and meaner, and ready to take you to the winner's circle!

A lighter crankshaft, with DLC coating, Tungsten weight and silicone-filled intake passage
Modified piston and con rod that reduces overall weight
Newly designed outer head with V-shaped fins for lower CG and more efficient cooling
Dual-adjustable 21J carburetor for smoother acceleration and better fuel mileage
A 6.5 mm restrictor is installed; 6 mm and 7 mm restrictors are included

The O.S.SPEED 21XZ-B has been supported by many top drivers worldwide due to its high performance and achieving excellent results at many major races including podium positions at the last two World Championships.
New drop-in type outer head with special laser marking contributes to lower CG and better cooling efficiency. Each inner part has been modified for smoother acceleration up to top speed. New lighter piston and connecting rod contribute to better response to driver's throttle operation. Lighter DLC coated, tungsten weight pressed-in and silicone potted crankshaft reduces friction loss further. Further evolved O.S.SPEED 21XZ-B Spec.II is born to win big races.

• New lighter piston and connecting rod
• New crankshaft features lighter weight, DLC coating, tungsten weight and silicone potting for optimum rotating mass
• New outer head features low CG and better cooling efficiency.
• Well-established 21J double-adjust carburetor is employed. 6mm, 6.5mm and 7mm restrictors are supplied as standard