FREQUENTLY ASKED QUESTIONS
What is the engine weight installed and ready to run?
Electric Fuel Pump: "My
fuel tank is approximately 20 to 25" below the 700e carbs. Would I need
a electric pump?"
121 lb plus oil, propeller, engine mount.
Yes The engine comes standard
with a pneumatic fuel pump which operates from pressure pulses. If the
fuel supply is below the level of the carburetors, a backup electric pump
must be installed.
Hearing different stories about the power
and idle speeds...
Idle speed is between 1800 and
1950. Most we have seen like to idle smoothly around 1900. A lower inertia
prop might allow lower. For instance, our Kitfox with an Ivo In-flight
Adjustable will idle nicely at very low rpm, ...like 1400. We like to think
this, in part is because of our mount, but at flat pitch and low throttle
setting, the propeller puts very little load on the engine. Our Zippy Sport
with a very steep pitch 2 bld 64 inch prop likes to idle around 1900.
What would be your recommended propeller?
There is no "Best Propeller" Brand preference plays some part
in selection, as well as price, but the application is what really determines
Diameter, Number of Blades, and preferred Gear Ratio.How
many pounds of thrust can I expect?
Power Nothing is absolute. Much of
our data comes from tests with GSC Systems propellers. The number
values may be different with other propeller designs but the principal
is the same. Also, performance difference between Rotax 2.62 type C and
E gearboxes vs the 2.58 type A or B is insignificant. Power output of the
HKS 700-e is just off that of a Rotax 582. The challenge for some, especially
PPCs is how to convert that power to static thrust. For instance: A Trike
owner replaced a 50 HP Rotax 503 3.47 E box engine with a 60 HP HKS 700-e
and 3.47:1 ratio. He used the same large diameter Ivo 3 blade propeller.
Without adding pitch, the HKS could easily over rev. ...A clear indication
of increased power. Eventually he was able to crank in enough pitch to
load the engine with a resulting take off and climb similar to the 503,
but with much faster cruise speeds at low rpm. Static thrust was not substantially
improved because the extra pitch to load the engine made the prop less
efficient for producing static thrust.
HKS vs Rotax. The propeller doesn't care
what turns it. So it is a matter of Diameter, Pitch, Speed, and the variations
in efficiency. Our Rotax experience suggests a 2.58 or 2.62 ratio gearbox
on a Rotax 503 is best configured to produce static thrust with a 60 inch
3 blade propeller. If a two blade is used, and pitch is increased to load
the engine, static thrust will suffer. So a two blade either has to be
longer or turn faster. To achieve equal or better static thrust,
than the 60" x 3 bld prop and 2.62 ratio, but with two blades, and
the same ratio, 68 inch diameter is near optimal. Another possibility is
faster prop speed. A 60 inch two blade can work just as well as a 60 inch
three blade on a 503 if it's turned faster using the 2.238 ratio. So, if
the non variable is 60 inch propeller diameter and the goal is to increase
static thrust by adding 10 HP, results will be far from linear. In testing
Rotax 503 vs 582 using 60 inch three blade propellers, the 30 percent increase
in Horsepower resulted in less than 10 % increase in static thrust.
The HKS with 2.58 and 64 inch GSC Tech III prop
will produce nearly identical thrust as a Rotax 582 with 2.62 and 60 inch
GSC Tech III prop.
What's the deal with the oil hoses and fittings?
Do I need the measurements and get them cut to fit, or just order the fittings
and attach the hoses myself?
You will make up the individual line from bulk length of hose.
The AN-10 fittings are barbed on one end and require no special tools to
assemble. Once a specific length and fitting angle are determined, we generally
freeze the fitting, and warm the oil line. Joining the line and fitting
is pretty much a continuous one shot deal. If the line is pushed on only
part way, it is very difficult to start again and push it fully in place.
It is basically impossible to remove without cutting the line. If you have
to do this, be careful not to mark, or otherwise damage the fitting.
I thought the exhaust pipes came with the nut (for the EGT probe) already
welded on. Mine don't have them.
Small hose clamp senders are used for EGT. The factory pipes
are Stainless, so you could TIG weld bosses if desired, without much discoloration
of the pipe.
Why are there no mounting bolts for the engine? Can I order
them from you?
The mounting bosses on the HKS are well above the lowest point
of the engine (the crankcase sump). The length of bolt will be determined
by the individual application. The universal plate that is available stands
off a minimum of 9/16 inch. This can mount with bolts as short as 50 mm.
With longer spacers, obviously longer bolts are required. An important
detail, is the thread pitch. HKS and Rotax both use 10 mm diameter fasteners
for mount attachement, but he HKS is a 10 mm x 1.25 fine pitch vs 1.5 coarse
pitch for the Rotax. These metric bolts are generally available locally.
If that is not option, let us know what length you would like, and we'll
get some for you. We generally have a variety of lengths in stock.
Is it true: If the battery dies the engine will quit?
The HKS uses a DC CDI. This type of ignition allows a full
advance curve, without which the engine would be very mediocre in most
respects. It must have 12 volts DC from an outside source to start. Once
running, a dead battery will not effect engine operation because the integral
alternator will provide power for ignition. The concern, then becomes one
of wiring. Output from the charging system needs to be on the line side
of the circuit which powers ignition. This way, regardless of battery,
cable, or master switch condition, primary power is uninterrupted. In the
event of a charging system failure, ignition is dependent on battery.
I know the muffler needs to be shock mounted...Do the exhaust pipes
need to be secured to the engine (other than
at the exhaust ports)? It looks like they might twist/turn/vibrate
and break the weld...Has this ever been a problem?
Generally, this has not been a problem, but it has happened.
Securing the exhaust pipes to the engine may actually do more harm than
good. Naturally, the individual engine installation can effect the outcome,
but the stock systems have been well proven. Particularly, the Type II
as used on the Flightstar. It has 2 slip joints to a collector, then a
ball joint to muffler, and a final vibration dampened attachment to the
airframe structure. Of course, in pusher application every reasonable precaution
should be made with safety restraints on anything that might depart the
aircraft forward of the propeller. Green Sky Adventures, Inc. manufactures
alternate exhaust systems designed around specific HKS / Airframe installation
packages. Besides "Best Fit" for the particular installation, there are
other benefits to such a system. We use a readily available industrial
muffler, and build up head pipes generally from Mild Steel U-bends (Stainless
can be used). Field repairs or replacement may therefore available locally,
eliminating any possibility of extended lead times for specialty OEM parts.
Our systems have proven durable, with equal performance, good sound, and
comparable or less weight.
Can the HKS700 E operate on oxygenated gas ? This is the only
type available here in northern Illinois?
The engine and carburetor components are compatible with present
oxygenated fuel. If percentages increase, it is logical to expect a possible
rise in exhaust gas temperature which can be compensated with larger jets.
Other components in the fuel system may or may not be tolerant. ...Gaskets,
o-rings, rubber seals, fuel level senders, tank floats, etc. ???
If in doubt, though more expensive, 100LL Aviation Fuel would be a good
choice. Lead contamination of the the oil in the HKS is not the concern
that it is with Rotax 912 because of the design of the oil system.
What is the Standard Equipment that comes w/ the HKS 700E?
Challenger: How involved is taking off the wings for trailer transport
if the HKS is mounted on the topside as with the Green Sky top mount solution
Carburetors, Air Filters, (choice of high or low mounted carburetors),
Fuel Pump, (pneumatic type. electric backup is required if
fuel supply is lower than carburetors) Gearbox, offset up or down with
choice of 2.58:1 or 3.47:1 (ratios NOT interchangeable), Dual CDI Ignition,
Sparkplugs, Regulator / Rectifier, Electric Starter
Required options: Oil Tank, Oil Cooler, Eight AN-10
oil fittings, (12 if using oil thermostat) Exhaust (custom
systems can be fabricated. 1.125 dia. Two into one is preferred. Bend sections
(mild steel) are available at Green Sky Adventures, Inc. )
What is the advantage of using an oil thermostat?
As of Feb 2007, the exhaust and oil cooler mounting details have not been
frozen. These are planned to be supported from root tube bases. The gap
cover obviously must be trimmed to fit around these accessories. If cowled,
the cowl will have to be removed prior to wing removal. Aileron linkage
can disconnect at the control horn, then wing removal involves spar and
strut attach points.
Which additional fittings would be required to mount the thermostat?
The thermostat will divert oil flow, bypassing the cooler for faster
warm up. In cold weather, it also serves to maintain safe oil temperature.
An alternate solution is to construct a system to manually control air
flow through the cooler. In some applications, diverting oil cooler air
to the cabin for cabin heat may be worth consideration. The Oil Thermostat weighs 1.5 lb, plus 4 additional fittings, and extra oil line. Advantage vs no advantage may be a personal preference.
Why a 19-row oil cooler as opposed to the 25 or 16 row?
The oil thermostat requires 4 additional AN-10 fittings. Which ones can
only be determined on the individual application. Green Sky Adventures,
Inc. does not currently incorporate an oil thermostat in our installations.
How effective is the Carb Heat Probe? Is it used similar to a
Carb Heat on a conventional airplane?
The cooler size needs to be adequate to allow good cooling even in extreme
climates, but no more. Any excess capacity is unnecessary weight and expense.
The design of the HKS-700e makes it one of the easiest engines to cool,
that you might ever encounter. The range of available sizes is an attempt
to cover most possibilities. In tractor configuration, the 16 row cooler
(235 mm length) placed in direct prop blast provides more than enough cooling
in nearly every circumstance. The same cooler may also work well on tractor
applications if mounted slightly out of prop blast. Often, the overall
dimensions of some installations may dictate an oil cooler location where
air flow may be more questionable. In such case, a 19 row or larger might
make up for that shortcoming. Remember, it is easy to block air to get
temps up. FYI, One manufacture now supplies the 16 row x 115 length cooler
for their tractor mount HKS. In pushers, the 19 and 25 row are most
common. Click HERE
to view oil cooler dimensions.
I read a little on the HACman
mixture control. It seems pretty nice and a good tool if you
are flying at altitude. Is there any additional instrumentation required
with this installation?
The electric probe warms the carburetor body. It is generally used as a
preventative. Unlike Carb Heat systems of conventional aircraft it is commonly
left on continuously when operating in climate conditions where carb ice
is possible. This does draw from the available electrical power. If running
strobes, nav lights, transponder, com radio, etc. it may not be possible
to maintain a positive charge rate. (17.5 amps at 12V) Because of the short
intake track of the HKS, carb ice has not been as common as with a Continental,
for instance. Remember, the cylinder head, to which the intake tube is
bolted is running about 300 degrees F. Header wrap is sometimes used to
insulate the intake runners effectively warming the carburetors. Alternate
solution to deal with potential carb ice would be to pick up hot exhaust
air and duct it to the carburetor Body. Conventional ducting through the
intake is not a preferred method to deal with carb ice on the HKS
What are the DC toggle switches for?
Monitoring Exhaust Gas Temperature is a requirement.
In particular, what hardware does not come with the Challenger Mount?
The HKS uses a DC CDI. It must have 12 V positive supplied for starting.
Once running, the integral alternator will power the ignition if battery
fails. Regardless, the ignition switching circuit must be closed for operation
and open for shut down. So, a high quality switch is required. A conventional
aircraft switch with Off, Left, Right, Both, Start, will not work, because
these open the circuit for "on" and close it for "off". Consequently,
high quality DC toggle switches are required. In order to have a
keyed system, Green Sky generally recommends a conventional Old style
automotive key switch with Accessory, Off, On, Start, positions. This can
easily be wired as a keyed master / start switch. With the reg rec and
ignition lead wired to the IGN terminal, 12V+ is supplied for ignition
via the battery when the key is turned to on or start position and via
the integral alternator regardless of key position.
Eventually our goal is to have installation kits complete to the point
that a technician can be locked in a room with the subject aircraft and
our kit and need nothing else to finish the job. That goal may be overly
ambitious. As of Feb. 2007, we have developed basic mounting systems for
various popular aircraft, including the Challenger. Not included at this
Working with individual builders, each of these items will eventually be
addressed. All of these can have simple solutions but with a little extra
effort on our end, standardized components will have uses on various similarly
configured aircraft. We have worked and are continuing to work with customers
over great distances on Challenger, Kolb, Quicksilver, Rans and others.
Is the remote electrical accessory connector kit the same thing as a
Stantion supports and mounting for the muffler, and oil cooler.
Mounting for cdi modules, reg rec, ignition coils and oil tank
Aileron Control system modification.
Are the oil filters proprietary or are they readily available locally?
Not until the wire is added. The Electrical Accessory Connector kit includes
the solderless connectors and housings that match those already on the
engine from the ignition triggers and the alternator. One could technically
use high quality Molex connectors, these are just a bit better, and will
save a few trips to town. We normally include these when quoting an engine
or installing one. For close in firewall mounts, you can plan out the installation
where the EI boxes, coils, and RegRec will hook up with their existing
cable. Similar is possible with Kolb and Challenger
Are there air and oil filters included?
Oil Filters are automotive type and can cross reference with many manufactures.
Wix 51394, and Hastings LF410 are a couple
Are there recommended accessories that are added cost?
Yes, Yes, K&N Conical style.
Possibly the most important question would be the cost. How much
will it cost me?
Yes. Start with the base price of the engine. The engine comes with airfilters,
electric start, Regulator Rectifier, Dual DC CD Ignition, and Integral
gearbox. Add oil tank. (Though you theoretically can supply your own tank,
HKS won' t warranty the engine with an alternate tank at this time.) Add
the appropriate exhaust system style. (An HKS factory system is best unless
it compromises the finished installation because of size or shape) Add
the appropriate oil cooler, fittings, and oil line. The list of additional
items can go on and on, depending on what you're starting out with. Starter
Solenoid is not included. If fuel supply is below carburetors, a back up
electric fuel pump is required. For an itemized list of most components,
see our Price
What oil is recommended for the engine? The PSRU gearbox, if separate
from the engine?
The variables are many, like exhaust style, mount, instruments, control
cables, oil cooler size, fittings, etc. As of March, 2008,(and continuing in 2013)a typical package
is running between $11,000 and $12,000. For instance, a complete package
for Avid is just under $11,400, including motor mount, and custom exhaust.
We just sent out a complete mounting package and engine for a Kolb. Bottom
line $11,631. For the most part, if you are starting from zero, an HKS
is priced vary competitively with a Rotax 582. We also take Rotax
What fuel is recommended?
Automotive full synthetic 0w40 is approved for all climates. 5W40 and 5W50 is approved from about 20 degrees F and higher. 10W50 is approved for 50F and higher. Mobile 1, Royal Purple, etc. Gearbox is integral
with engine and oiling system.
Do you have a firewall forward package available?
92 Octane RON minimum. Premium auto fuel, or 100 LL Aviation Fuel
.Is 1000 hours reasonable for TBO?
We have installation components available for Avid Flyer, Challenger, Fisher
404, Fisher Super Koala, Fisher Dakota Hawk, Kolb, Hiperlight, Kitfox,Micro Mong 2XF, Rans S14 and S12, Quicksilver
Sprint, Sport, and GT, Zenith 701. We have inhouse cabability to produce firewall
forward for most any design
What does a TBO rebuild consist of?
Yes, but engines from sr no. 100300 to 100599 are officially 500 hr TBO.
I don't know of anyone with this series engine who is overhauling at that
number of hours. Engines from sr no. 100600 up are 1000 TBO.
That is a realistic recommendation.
Can the rebuild be accomplished by a person with good mechanical skills
( I have rebuilt several auto engines including a VW and Rotax 582 with
What is the cost of parts for the rebuild?
There is an overhaul parts kit that includes: All seals and gaskets, new
intake and exhaust valves, pistons, rings, wrist pins, main and rod bearings,
oil filter, spark plugs, and carburetor insulators. This does not
include carburetor rebuild.
Are machine shop services required or special tools? If special
tools, are they available?
Overhaul kit runs $1484. as of March 2010
What is the Cost for Green Sky to do a rebuild?
There is a breakdown of tools in the service
manual. A reasonably well equipped engine shop may already have equivalent
tools to facilitate a quality rebuild
I bought a hks 700E with serial no between 100301 and 100600 I would like to know the tbo of this engine Did I BUY A GOOD ENGINE IT IS BRAND NEW
A conventional overhaul as described in the service manual is currently running slightly less than $3,000. This includes set up and test time following the service. Two of the last seven engines we overhauled required replacement of heads, nearly doubling the cost of overhaul. The other five were 100 percent text book. All but one were over 1000 hrs.
That pricing excludes fuel system and incidentals. Shipping could be done by UPS. The
shipping weight is generally less than 150 lb. Conway express is currently
an effective carrier on new engine deliveries.
Yes! Sr numbers between 100301, and 100599 are good engines. They are not among the early group that was recalled many years ago. The recommended hours TBO for yours is 500. After sr number 100600, there were some small changes made to exhaust and intake ports, and other small changes during serial production. This later group has a recommended hours TBO of 1000. If your engine has never been run, and has been stored well, it should be a very good engine for a long time.