The O.S. MAX-140RX is a legendary, vintage 23cc (1.40 cu. in.) two-stroke nitro/glow engine designed specifically for FAI F3A precision aerobatics (pattern flying). It was introduced by O.S. Engines to capitalize on F3A rule changes that permitted larger displacement two-stroke engines.
Displacement: 23.0 cc (1.404 cu. in.)
Power Output: 3.5 horsepower (ps) at 9,000 RPM
Practical RPM Range: 1,800 to 10,000 RPM
Weight: 807g (28.5 oz)
Exhaust Configuration: Rear exhaust (designed to seamlessly tuck a long tuned pipe into the fuselage of a pattern plane).
The “Pumped” Fuel System
Unlike standard glow engines that rely on muffler pressure to push fuel out of the tank, the MAX-140RX features an integrated regulated pump system. It uses a specially designed O.S. Type 70A carburetor paired with a Type PD-06 diaphragm fuel pump
The Benefit: It isolates fuel delivery from the physical location of the fuel tank and aircraft attitude. Whether you are flying straight up, inverted, or performing complex tumbling maneuvers, the engine receives completely consistent, bubble-free fuel pressure without relying on muffler backpressure.
Propellers: It is designed to turn large, high-pitch props at low RPMs to limit noise. Popular choices include APC 16×12, 16.5x12W, or APC 17×12.
Fuel: It thrives on high-quality fuel containing 5% to 15% Nitromethane with an oil content of roughly 15% to 20% (often using a blend or pure synthetic oil).
Glow Plug: It is typically paired with an O.S. Type F plug.
Maintenance: Because nitro combustion produces corrosive updates, it is highly critical to use after-run oil through the carburetor after every flying session to prevent main ball-bearing and crankshaft corrosion
