We are pleased to introduce the MAX-21XZ-B Ver. II for drivers who demand performance close to that of our flagship model, the O.S. SPEED 21XZ-B spec. II but at a more affordable price. Many top drivers around the world choose O.S., relying on the renowned linear acceleration to get the best power at the right time. We developed the MAX-21XZ-B Ver. II based on the O.S. SPEED 21XZ-B Spec. II but adopted a single-needle carburetor for easier adjustment. We use the same piston/liner and connecting rod from the flagship model, the O.S. SPEED version, in the new MAX-21XZ-B Ver. II. The crankshaft has the Tungsten counter weights similar to the O.S. SPEED, but without the ultimate DLC coating, offering superb value for money.

The newly developed 22B2 carburetor, which determines the high R.P.M. characteristics of MAX-21XZ-B Ver. II, gives first priority to ease of use. A 7mm diameter carburetor reducer is included as a standard accessory. The low, centre of gravity outer head is anodized in the traditional O.S. blue color.


This latest engine in the O.S. off-road range is the next step in O.S. market leadership by offering improved performance and technology at the right price.


Displacement: 3.49cc
Bore: 16.27mm/ 0.641in.
Stroke: 16.8mm/ 0.661in.
Practical RPM: 4,000~42,000r.p.m.
Power Output: 2.65ps/33,000rpm /2.61hp/33,000rpm.
Weight: 355g/ 12.52oz.