The 700E was designed to get two-stroke like power output from a four-stroke engine. The way to get more power from a given size engine is to make it do more work, meaning more RPM. The operating RPM range of the 700E is normal for an engine using modern motorcycle technology. The Rotax 912 four-stroke has a similar operating range.  

Why does the HKS have a gearbox, isn’t direct drive lighter and simpler?

The larger the propeller, the more thrust it will produce, particularly at the relatively slow climb speeds of light aircraft. More low speed thrust means more climb. As well, there is the great benefit of much lower propeller noise than direct drive. The 700E gearbox has two ratios available 2.58 and 3.47 to.

Can the gearbox be positioned up or down? Is it a big deal to swap the position? Can the engine be run inverted?    

The gearbox can be positioned up or down. To change the position the front cover is removed and rotated. The HKS 700E cannot be run inverted.

How do you change the gearbox position? 

The attached set of instructions will step you through the process.  The following list of parts will be needed for the job: 
04Y-457  GKT COVER FRONT 1 needed (If the engine serial number is 100600 lower, contact us for a special gasket)
04Y-224  GKT REDUCTION Type A 2.58 Gear Box 1 needed (04Y-225 for a Type B 3.47 Gear Box)
04Y-409  WASHER 1 needed
04Y-399  NUT CRANK M25 1 needed
Instructions for changing the gearbox at this link. 

 Why does the HKS have separate oil tank? And what is a dry sump engine?   

The 700E has a separate oil tank to reduce the package size of the engine. Most conventional aircraft engines are dry sump for the same reason. A wet sump engine has it s oil supply in the oil pan at the bottom of the engine. A dry sump engine has a separate scavenge pump to take the oil from the bottom of the mini-sump at the bottom and a supply pump to send oil under pressure through the engine.  

Can the HKS engine be used in pusher installations?  

Yes. As a matter of fact the 700E has been designed to work specifically in both the pusher and tractor configurations. A majority of the hundreds of engines sold are operating in the pusher configuration. 

What type of fuel does the HKS require? Can it use 100LL?    

Automotive Unleaded-high test is best. 92 octane Unleaded is typical. 100LL Avgas can be used during cross countries without worry. Constant use of leaded fuels requires different lubricating oils to be used to avoid lead deposits.

What is the fuel consumption of the HKS?

The fuel consumption in typical operation is between 2 gallons and 3 gallons an hour. In our testing, the fuel consumption we have noted is 2.5 gallons an hour @ 75%. The Dyno testing according to the JIS (Japanese Industry Standard) requires the engine to be tested in a manner that does not reflect propeller loading. This makes HKS s consumption numbers very conservative.

What type of exhaust is required? Can you run straight pipes? 

The 700E was designed as a complete system. There are requirements for back pressure and length of the exhaust manifold as a part of the system. Both the intake and exhaust manifolds are optimized for a flat torque curve.

Are the carburetors used on the HKS altitude compensating? Why don t they use Fuel injection?

The Bing C.V. (Constant Velocity) carburetors are capable of 50% mixture compensation to approximately 10,000 Ft. due to the CV design which uses a diaphragm-slider to vary the mid range mixture. The Rotax 912 four-stroke uses the same carburetors.

How much does a complete engine package cost?

Air Parts Sales Unlimited will sell a 700E as a complete system. We will help you choose the best accessories and we will help you with custom applications.   We will also provide complete service and support for existing engine owners.

What is the warranty on the HKS 700E  

The Warranty for the HKS 700E is one (1) year or 100 hours of engine time.

What type of engine mount does the HKS have? Do you sell mounts?

The 700E has a base mount similar to but slightly different than the Rotax. There is also a requirement that the engine mount have a hole for in the center for the sump to fit into. We can work with you with on the design requirements.  We feel that this is the best way as they know their planes requirements.

What type of propellers work best for the HKS? Are they readily available?

Yes, The Powerfin "F" model propellers work well. Another propeller is the GSC from Canada.

What is the TBO for an HKS 700e?

For Engines with Serial Numbers from 100600 and higher, the TBO is 1000 hours (Updated from 800 hours on December 26th, 2008).  For all older engines, the TBO is 500 hours.  Please refer to Service Letter SL-0801 for details.

Can the HKS-700E be run without a prop?

According to the factory, yes, the HKS-700E can be run without a propeller for the purpose of carburetor balancing and to check the operating condition of the engine for new installations.  ALWAYS USE CUATION.  Since, without a propeller, the idle speed will have a tendency to run higher, the idle may have to be adjusted down.  Without the propeller, it will also be very easy for the engine RPM to increase excessively, please be careful when adding power with the throttle.  Keep this type of operation to a minimum.  Use extra caution to not over power or “rev” the engine under these circumstances as over speed could harm the valve train.  Also, expect EGT to be abnormal when running under these conditions.

All of the bolt torque information is in metric (kgfm – kilo grams force meter), how can we convert this to ft lbs?

The conversion factor is: 1 kgfm = 7.233 ft-lbs. In most of the HKS documentation distributed in the US, we’ve tried to add in ft-lb units where torque values are given.  We appologize if we've not been able to get to all the documentation yet.  

 When ordering engine parts, how do I know what side of the engine is the right side and what will be the left side.

Right and Left are as seen from standing from the back of the engine at the oil pump side looking forward.

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HKS Exhaust System Application Notes