why HKS
Green Sky Adventures, Inc.    of North Central Florida
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Why 4 Stroke, Why HKS

 
A new version of the HKS four-stroke engine used in Light aircraft, PPC?s and Trikes is now being delivered in the U.S.In development and testing for nearly two years,the new 700E has improved cooling performance and has been further optimized for pusher applications.
Over 20 airframe manufacturers worldwide now offer the HKS-700E for their aircraft. 
The HKS 700E is a 60HP, horizontally opposed, two cylinder, four-stroke engine.The 700E uses a combination of high technology and simplicity to achieve the twin goals of high power output and reliability. The 700E is a very high quality product.Every major component was designed for light aircraft use and is made from the best materials and techniques available.
In power to weight ratio, the 700E matches conventional two-strokes.The real difference, however, is in the high peak torque (62ft.lbs) of the engine and the very flat torque curve.This allows the 700E to pull better in a climb or hold a higher prop load (pitch) than the 60 horsepower rating would suggest.
The integral gearbox on the 700E uses straight cut gears with a spring-washer type torsional coupling ahead of the large flywheel.The gearbox is attached to the flywheel case; the gears are lubricated by the main engine oil system, the same as a Rotax 912 four-stroke.The gearbox can be run up or down and is changed by rotating the flywheel case around.The large flywheel mass and attention to the internal balance of the engine are the keys to the smooth running and low vibration of the 700E.At a lower RPM you can hear the gears singing, not clattering.The standard gear ratio is 2.58 to one. As the Max permissible RPM is 6200, the RPM at the prop is 2400.With the optional 3.47 to one gearbox, the prop speed and noise is even lower.
The prop hub bolt pattern is the popular 75MM pattern; the direction of rotation is the same as a Rotax two-stroke.Baseline tests have been conducted of several popular propellers, including the Ivo-prop, Power-fin and Sport props.In tests, the 700E can swing a 74? two blade and a three blade 68? was typical. The engine was just as smooth with a two blade prop as three. This also allows the use of a light, wood two-blade for certain applications. 
The induction system of the 700E has been optimized for a wide torque band. The runner lengths are tuned for this purpose.The carburetors are the Bing Constant velocity type, which varies the mixture with horsepower and provides a modest amount of altitude compensation. These are the same carburetors used on the Rotax 912 four-stroke.
The valve train of the 700E is operated with pushrods off of a single, centrally located camshaft; valve lash is adjusted automatically with hydraulic lifters.The crankshaft and connecting rods are forged, and run in split shell-type bearings.During overhaul the crank and connecting rods won?t have to be replaced, just the bearings.The cylinder bores are Nickel-ceramic coated for wear resistance and thermal compatibility with the expansion of the piston.
The dual CDI (Capacitive Discharge Ignition) is a programmed smart type that varies the timing for ease of starting, smooth idle and detonation resistance.The connectors to the electrical system are large sealed type and can only attach to the correct component.The charging system is 15 Amp-180 Watt.The exhaust systems that are provided in the complete packages are beautiful.Made from highly polished stainless steel, they come in four configurations (two manifold types, two mufflers) and can be modified with optional stock components.HKS is a big producer of performance exhaust systems for all types of cars and their expertise clearly shown in the design and fabrication of the manifolds and the mufflers.
The 700E has been tested on a Flightstar-IISL testbed since July?97 and the results have been impressive.The engine has been easy to start, very fuel efficient and reliable in operation.The range of the Flightstar-IISL was effectively doubled with the switch out of the standard 503.The fuel specifics sent from Japan indicated a fuel burn higher than achieved in Flightstar testing; the factory spec is based on a constant peak torque load while dyno testing. This would be the equivalent of a very high pitch prop and full throttle. Flightstar testing with typical, fixed pitch propellers showed an average fuel consumption of between 2 and 2.5 gallons an hour at typical cruise settings.
The installation requirements are different for a four-stroke engine and Green Sky  is here to help with the choice of components and the design of mounting system.Green Sky  can supply you as well with the proper accessories like oil lines and fittings, instruments and service parts.We have done a lot of research on the various components available and are planning to be a worldwide leader for HKS 700E specific equipment. 
The 700E comes from HKS with detailed Installation and Operation manuals.A Parts manualas well as an Operations  and Installation manual are available on line.