O.S. MAX 50SX-H Ring Hyper (L-OS15550) The best 50-class engine on the market just became amazing with the introduction of the new 50SX-H Hyper. That CNC machined cylinder head has been developed to give better power & enhanced cooling at the same time. The new carburettor has also been enhanced to help extract more power than the standard engine without sacrificing the throttle precision you have come to expect from OS helicopter engines. This truly is the best engine in the 50-class & is fast becoming the best seller as well. Its an OS, what else would you expect!! Specification: Weight: 413g Bore: 22.0mm 0.866in. Stroke: 19.6mm 0.772in Power Output: 1.8/17000 (BHP/RPM) Practical RPM: 2000-20000 ...

O.S. MAX 55AX w/E-3070 Silencer (L-OS15611) Designed to combine maximum power with razor-sharp throttle response in the smallest possible crankcase, the 55AX has the same mounting

Dimensions as the popular 46AX but with more power. The dramatic AX fin styling is used for optimum cooling, & the rearward-angled needle on the the type 40J carb makes for safer adjustments. Perfect for sport, scale & aerobatic appplications. Specification: Capacity: 0.54cu. in. (8.9cc) Bore: 0.91" (23mm) Stroke: 0.85" (21.5mm) Weight: 14.25oz (404g) (w/o silencer) Power Output: 1.75hp @ 16, 000rpm Practical RPM: 2, 000
- 17, 000 Propeller Range: 12 x 7"
- 8", 13 x 6"
- 7" Silencer: Power Box E-3070




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O.S. MAX 55HZ Hyper (L-OS15630) The max 50SX-H Hyper has established an enviable reputation for power, reliability & ease of use. The Max 55HZ Hyper moves that to a whole new level! Designed primarily with the demands of the 3D pilot in mind, the 55HZ Hyper delivers 61 size performance in a 46 size crankcase. That power comes from the extensive experience that OS has gained over many years & working extensively with the worlds top pilots to refine all aspects of the engine without compromise in any area. By using the same mounting layout, you can drop a 55HZ into any model that previously suited the 50SX-H without modification. Just the area around the new carburettor is a little bigger & may require adjustmenst to the cooling shroud. This entirely new engine shares almost nothing with the 50SX-H & has some new features not seen on an engine of this size before. The rear bearing is now designed to resist corrosion, the new 40L carburettor has three adjustments to cater for idle, mid range & full power. Until now, these features were the domain of 61 class engines or bigger. The throttle arm has four leaves so that push pull control is easy from any direction. The heatsink head is bigger for enhanced cooling as well. For the first time, OS is also offering a matching tuned muffler as an option part & has been optimised to extract the maximum performance from the 55HZ Hyper. Part number X-OS72144000. Specification: Weight: 408g (14.39oz) Displacement: 8.93cc (0.55cu.in) Bore: 23mm (0.91in) Stroke: 21.5mm (0.85in) Power Output: 2.1PS @ 17000RPMPractical RPM: 2000
- 20000
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O.S. MAX 55HZ Hyper Engine & Silencer
- Ltd. Ed w/ Pipe (L-OS15637) A special limited edition version of the fabulous Max
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O.S. MAX 55HZ-R Engine (L-OS15650) The latest engine in the 600/50 helicopter class borrows much of its technology from the fabulous Max 91HZ-R, to provide class leading power under the most demanding of 3D manouevres. The latest DRS system (Demand Regulator System) uses a crankcase pressure tap-off to pressurise the fuel tank via a one way valve. The pressurised fuel is then carfully regulated at the carburettor to provide the optimum mixture no matter what demands are placed on it. This is done by using the negative pressure in the carburettor venturi as part of the regulation system. The carburettor itself has three mixture controls for low/mid & high speed settings. Once set for the fuel demands of your model/type of fuel & muffler, there is rarely any need to change those settings again. The main mechanics of the engine itself are the same as the regulat Max 55HZ. Specification: Weight: 429g (15.13oz) Displacement: 8.93cc (0.55cu.in) Bore: 23mm (0.91") Stroke: 21.5mm (0.85") Power Output: 2.1PS @ 17000rpm Practical RPM: 2, 000
- 20, 000
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O.S. MAX 75AX w/E-4040 Silencer (L-OS17400) The third engine in the new ‘AX’ range of high performance two-stroke engines fills a convenient gap between the existing 61FX & 91FX, yet features the radical new style pioneered with the fabulous 55AX. The new 75AX is supplied complete with the latest ‘P-Box’ design silencer for enhanced noise suppression. By keeping the lower crankcase

Dimensions the same as the 61FX, you can be sure that it will fit in all models designed for a. 61, making a power upgrade very simple. The 75AX features the latest O.S. ringless piston technology with multi-layer cylinder coating & high precision Type 61A carburettor with angled safety needle valve assembly. Specification Weight:578g / 20.39oz w/o silencer Capacity:12.29cc / 0.75 cu.in. Propeller Range:13x 8-10 14x 6-8 Bore:25.8mm / 1.016in Stroke:23.5mm / 0.925in Power Output:2.4PS @15, 000

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O.S. MAX 91HZ w/61E Carb Engine (L-OS18650) Identical in most techincal respects to the original Max 91HZ Ring engine but now with the latest 61E carburettor for an enhanced spread of power across the RPM range. Ideal for sports flying & F3C competition alike. You can rely on OS! ...

O.S. MAX 91HZ-PS Ring (L-OS18620) Designed primarily for the 3D flight & dramatic aerobatic manouevres. Compared to the old Hyper the new 91HZ-PS offers enhanced hovering stability as well as power at high speed to meet the further sophisticated 3D competition manouevres. A new design piston & crankshaft reduces vibration to provide further, stable torque over the entire RPM range. The rectangular heatsink head is completely included in the cooling shroud for better cooling. The black alumite finish with O.S. & 91HZ-PS logo impart a distinctive image. A Thermo insulator is installed on the carburetor mounting spigot & helps shut out engine heat to the carburettor, which in turn ensures a stable fuel/air mixture. The 91HZ-PS is equipped with a new, bigger capacity PD-08 pump & matched 61B-P carburettor plus integral regulator, which assures a consistent fuel supply irrespective of violent changes in model attitude. Combined with O.S. pump system, internal parts improvements same as the 91HZ contribute to stable power output & smoother higher engine performance. Specification: Weight: 635g Displacement: 14.95cc Bore: 27.7mm Stroke: 24.8mm Power Output: 3.5PS @ 15000RPMPractical RPM: 2000
- 16000
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This version of the Max 91HZ series utilises a completely different system for supplying & regulating the the fuel supply to the carburettor & is called DRS (Demand regulator system). Unlike the Max 91HZ-PS, the Max 91HZ-R utilises a pressure bleed from the crankcase to pressurise the main fuel tank. The pressurised fuel feed is then regulated by a newly designed regulator that is well isolated from the heat of the engine through its mounting position. That regulated fuel supply is then feed into the new 61E carburettor. The serious 3D flier now has the choice between a mechanically pressurised fuel system (Max 91HZ-PS) or the tank pressurised system in the Max 91HZ-R. It is purely a matter of personal choice for the pilot. What other manufacturer gives you that level of choice in one engine size? Mechanically, the Max 91HZ-R is identical to the other engines in the Max 91HZ range. Specification Weight: 625g (22.05 oz.) Displacement: 14.95cc (0.912 cu.in.) Bore: 27.7mm (1.091") Stroke: 24.8mm (0.976") Power Output: 3.4 hp @ 15, 000 rpm Practical RPM: 2, 000
- 16, 000 Manufacturer: Ripmax Model: O.S. MAX 91HZ-R Ring (L-OS18640)
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O.S. MAX 95AX w/4040 Silencer (L-OS19120) Designed to replace the 91FX yet retain the same mounting

Dimensions but

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