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O.S. MAX 120 AX RC Airplane Engine

26,999.99 23,499.99
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Perfect for 3D, precision and sport flying!

Admit it: if you could ratchet up horsepower without having to increase the mounting space, you’d probably jump at the chance. Well, here it is. The 120AX boasts 25% more displacement than a .91 (think of the bigger props you can swing!) — and bolts into the same space, with almost no extra weight. And that’s not all. The 120AX’s innovative Power Box muffler offers mounting versatility that translates into value. Plus, the angled heat sink head not only looks sharp, it adds more surface area, for better cooling. Here’s a golden opportunity to boost your airplane's flying capabilities — with almost no modification!

O.S. Engines two year limited warranty
O.S. 120AX Ringed w/Muffler - Muffler
With the 120AX, there’s no need to buy an expensive aftermarket muffler!
O.S. 120AX Ringed w/Muffler - Power Box
The included Power Box comes with two adapters — one of which turns the muffler 90° to become a “Pitts style“.
O.S. 120AX Ringed w/Muffler - 1.20 Size
With the 120AX and .91 side by side, you can see how they’re virtually identical in size — but you’ll enjoy a big difference in performance!
Notes from our tech department:
This is the O.S. Max Two-Stroke 1.20AX Ringed Engine with Muffler.


Model Application: Ideal for 3D, Precision and Sport flying
Mounting Application: Mounts in same space as the .91FX (actual
mounting dimensions vary slightly, see SPECS)
Internal Construction: Steel piston ring and liner, aluminum piston
Muffler: E-5020 Power Box with extension and 90 adapters
Carburetor: 70D with rearward angled needle valve for safety
Glowplug: O.S. 8 supplied with engine, A5 (OSMG2693) will also work
Warranty: Two-year limited


O.S. Max Two-Stroke 1.20AX Ringed Engine with E-5020 Power Box
Muffler, 8 glow plug, muffler adapter, prop washer and lock nut,
needle valve extension cable,instruction manual and decal sheet,
two muffler screws, two muffler extension bolts, two long muffler


Fuel: Two-Stroke with 18 lubricant and 5-20 nitromethane
Propeller: 15x10-12 or 16x8-10
Field Equipment: Glow starter, fuel filter, fuel pump, fuel tubing


Displacement: 1.218 cu in (19.96cc)
Bore: 1.197 (30.4mm)
Stroke: 1.083 (27.5mm)
Practical RPM: 1,800 - 9,500 RPM
Power Output: 3.1 PS, 3.06HP9000 RPM
Weight of engine: 29.0oz (823g) with muffler
Weight of muffler: 7.074oz (219.2g) with 90 adapter installed
Weight of muffler: 7.907oz (245g) with extension installed
Crankshaft thread size: 516-24
Distance Between Mounting Holes Same Side: 0.98 (25mm)
Distance Between Mounting Holes Opposite Side: 2.3 (58mm)
Distance Center of Crankcase to End of Crankshaft: 4.3 (109.5mm)
Distance Center of Crankcase to Drive Hub: 2.7 (69.8mm)
Width Between Mounting Tabs: 2.6 (67mm)
Width of Crankcase Below Mounting Tabs: 1.8 (46.5)
Length from Backplate to End of Crankshaft: 5.5 (139.9mm)
Length from Backplate to Drive Hub: 3.9 (100.2mm)
HeightBottom of Crankcase to Top of Cylinder Head: 4.3 (109.2mm)
HeightBottom of Mounting TabsTop of Cylinder Head: 3.4 (85.7mm)
Distance center to center of muffler mounting holes: 48mm (1.89)

Needle Settings: High Speed: 2 - 2.5 turns out from fully closed
Low Speed: 34 turn out from fully closed with the throttle fully closed