O.S. Engine OSMG0650 120AX Advanced Airplane Engine  [OSMG0650]

O.S. Engine 120AX
Price:
£214.59
Brand:
O.S. Engine
Model:
OSMG0650
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Extra Displacement without Airframe Surgery

The 120AX from O.S. Engine slots into the same mounting area as a .91 unit but provides roughly 20% more displacement. That extra volume helps achieve stronger climb and prop loading without major airframe changes.

Compact Weight, Effective Cooling

At just 21 ounces (650 grams) the engine introduces little extra mass, preserving handling and balance. The angular head raises the surface area for improved heat transfer, aiding consistent performance across varied flights.

What Comes in the Box and Setup Tips

The 120AX uses CCD-compatible mounting and will replace many .91 installations. It is supplied with a #8 glow plug, a 70D dual-needle carburetor, and an E-5020 Power Box muffler with two adapters. Pilot favourites for props include 14x10 APC and 15x6 APC depending on the flying role.

Specifications

  • Displacement: 1.20 cu in (20 cc)
  • Bore: 1.197 in (30.4 mm)
  • Stroke: 1.083 in (27.5 mm)
  • Practical RPM: 1,800-9,500
  • Output: 3.1 hp @ 9,000 rpm
  • Weight: 21 oz (650 g)

The O.S. Engine 120AX is a pragmatic upgrade for experienced modellers seeking more thrust and flexibility while keeping installations straightforward.

Will I need to change my carburettor settings after installation?

Yes, initial needle adjustments are typical to match prop load and local conditions. Start rich and work toward a steady midrange and safe peak RPMs.

Is the 120AX noisy compared with similar engines?

Noise level depends on prop and muffler choice. With the supplied E-5020 Power Box muffler the sound is comparable to other high performance glow engines in this class.

Are spare parts widely available?

Common service parts such as glow plugs, gaskets and carb needles are generally available through established O.S. distributors and hobby shops.

What propeller should I try first?

A 14x10 APC is a good starting point for general 3D and sport flying; move to a 15x6 APC if you prefer a quicker, less draggy setup for fast aerobatic manoeuvres.

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