This is the Ultimate MXZ 3 Transfers Long Stroke .21 Engine with the Ultimate Airmax Air Filter. This engine is manufactured by the prestigious Japanese brand O.S. Engines, with the following characteristics:

Cooling Head

The MXZ is equipped with the same cooling head as its predecessors. This 8-fin cooling head has a very low center of gravity and has been designed to focus most of the airflow directly to the glow plug. By cooling the glow plug we get a more stable carburetion and idle.

Carburetor

Once again, the MXZ comes with the 21 J3 carburetor. Unlike the original OS carburetor, its high-speed needle holder was redesigned for better refrigeration of the fuel flow into the carburetor, lowering the temp of the carb, and consequently making it more stable with great idle stability, improved fuel mileage, and overall engine performance.

Besides this, the uniball joint of the carb slide was also modified with two stoppers instead of one. With this new modified design, you can easily adjust the angle of the uniball joint without having to disassemble the engine. This carb offers higher accuracy tuning, a very interesting advantage to experienced drivers.

Crankshaft

The MXZ comes with a 14mm crankshaft with a teardrop-shaped opening and paste in the inlet for improved flow.

Bearings

The MXZ comes with the original OS steel bearing in the rear and Ultimate Racing double-sealed steel in the front.

Venturi

The MXZ comes with the 6.5mm Ultimate Racing FLOWMAX venturi. With an innovative design, longer than the standard O.S. venturis and wider at the base, it ensures the inferior part of the venturi and the carburetor have exactly the same diameter. This new geometry improves fluid dynamics, providing extra power that allows the use of smaller venturis without decreasing power, and as a consequence, improves fuel mileage.

Sleeve and Piston

The sleeve with 3 inlet ports and an exhaust port guarantees low fuel consumption with very high but smooth and linear power. Both the sleeve and piston are made from a high-strength aluminum bar to improve durability.

Technical Specifications

• Displacement: 3.49 cc

• Bore: 16.27 mm

• Stroke: 16.80 mm

• Sleeve: 3 + 1 ports

• Practical RPM range: 4,000 – 40,500 rpm

• Max. power output: 2.55 hp at 34,000 rpm

• Weight: 350 g

• Crankshaft: 14 mm

• Carburetor: 21 J3

• Glow plug: P3 Turbo

• Exhaust Position: Rear