O.S. Engines
SKU:OS-18700
O.S. MAX-105HZ Helicopter Engine
O.S. MAX-105HZ Helicopter Engine
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High Power in a .90-Class Package
The O.S. MAX-105HZ is a high-performance 1.05 cu. in. nitro helicopter engine designed for pilots looking for serious power in a proven .90-class mounting footprint.
Developed specifically for 90-class RC helicopters, the MAX-105HZ increases displacement by approximately 15% compared with conventional .90-class engines while maintaining the same mounting dimensions. This allows pilots to gain additional power and torque without requiring major modifications to the helicopter or drivetrain.
A large velocity stack feeds cool air into the 61E carburetor to help the engine develop strong and consistent power characteristics. Combined with its lightweight machined aluminum heatsink head and optimized bore-to-stroke ratio, the MAX-105HZ is well suited for everything from smooth precision flying to demanding 3D aerobatics.
Key Features
- Powerful 1.05 cu. in. (17.17cc) displacement
- Same mounting dimensions as conventional .90-class helicopter engines
- Approximately 15% more displacement than a traditional .90-class engine
- O.S. 61E carburetor with large velocity stack
- Strong power delivery for precision aerobatics and aggressive 3D flying
- Machined blue anodized aluminum heatsink head for efficient cooling
- Compatible with conventional .90-class helicopter gear ratios
- Designed for use with the O.S. PowerBoost 105 exhaust system
Specifications
| Displacement | 1.048 cu. in. (17.17cc) |
| Bore | 1.142" (29mm) |
| Stroke | 1.024" (26mm) |
| Practical RPM Range | 2,000–16,500 RPM |
| Output | 3.7 PS / 3.65 hp @ 15,000 RPM |
| Carburetor | O.S. 61E |
| Weight | 21.03 oz (596.2g) |
Includes
- 1 × O.S. MAX-105HZ Helicopter Engine
- 1 × O.S. No.8 Glow Plug
- 1 × 0.1mm Head Gasket
- 1 × 0.2mm Head Gasket
MAX-105HZ or MAX-105HZ-R DRS – Which One Should You Choose?
O.S. offers two versions of the 105HZ platform. Both engines share the same 17.17cc displacement, 29mm bore, 26mm stroke and 2,000–16,500 RPM operating range, but the main difference is the fuel delivery system.
| Feature | MAX-105HZ | MAX-105HZ-R DRS |
| Carburetor / Fuel System | 61E carburetor with standard fuel system | 61G carburetor with O.S. Demand Regulator System |
| Output | 3.7 PS / 3.65 hp | 3.8 PS / 3.75 hp |
| Weight | 596.2g | 608.4g |
| Why Choose It? | A simpler, slightly lighter setup that still delivers excellent 105-class power and performance. | Adds regulated fuel delivery for pilots who want greater fuel consistency during repeated aggressive attitude changes and demanding aerobatics. |
Choose the MAX-105HZ if you want a powerful, straightforward and slightly lighter 105-class engine without the additional regulator system. For most sport and 3D pilots, it offers excellent performance with a simpler fuel setup.
Choose the MAX-105HZ-R DRS if you want O.S.'s Demand Regulator System. The regulator maintains a steadier fuel supply during rapid and repeated attitude changes, making it especially useful for demanding 3D and precision F3C-style flying.
Whichever version you choose, both engines deliver the displacement and power of a 1.05-size engine while fitting into a conventional .90-class helicopter installation.