Evolution Engines EVOE20GX User Manual

20cc

GA S/PE T ROL

Evolution® Gas Engines

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NOTICE

All instructions, warranties and other collateral documents are subject to change at the sole
discretion of Horizon Hobby, Inc. For up-to-date product literature, visit horizonhobby.com
and click on the support tab for this product.

Meaning of Special Language

The following terms are used throughout the product literature to indicate various levels
of potential harm when operating this product:

NOTICE: Procedures, which if not properly followed, create a possibility of physical property
damage AND a little or no possibility of injury.

CAUTION: Procedures, which if not properly followed, create the probability of physical
property damage AND a possibility of serious injury.

WARNING: Procedures, which if not properly followed, create the probability of property
damage, collateral damage, serious injury or death OR create a high probability of
superficial injury.

WARNING: Read the ENTIRE instruction manual to become familiar with the features
of the product before operating. Failure to operate the product correctly can result
in damage to the product, personal property and cause serious injury.

This is a sophisticated hobby product and NOT a toy. It must be operated with caution and
common sense and requires some basic mechanical ability. Failure to operate this Product
in a safe and responsible manner could result in injury or damage to the product or other
property. This product is not intended for use by children without direct adult supervision.
Do not use with incompatible components or alter this product in any way outside of the
instructions provided by Horizon Hobby, Inc. This manual contains instructions for safety,
operation and maintenance. It is essential to read and follow all the instructions and warn­ings in the manual, prior to assembly, setup or use, in order to operate correctly and avoid
damage or serious injury.

CAUTION: This product can become extremely hot when in use, which could lead
to burns.

Age Recommendation: Not for children under 14 years. This is not a toy.

Safety Warnings

Model engines produce a substantial amount of power, which can create unsafe situations if not
used correctly. Always use common sense and observe all safety precautions when operating,
handling or performing any procedure involving your engine. Failure to follow safety precautions
could result in serious injury and property damage.

• Always ensure spectators, especially children, are at least 30 feet away when running
the engine.

• Always ensure that the propeller is securely attached to the engine shaft and all retaining

fasteners are tightened properly before EACH flight. Use of blue threadlock to tighten nuts
is advisable.

• Always keep small parts out of the reach of children as they can be choking hazards.

• Always secure the airplane before powering the engine.

• Always keep your face and body away from the path of the propeller blades when starting

or running your engine.

• Always stand behind the propeller when making carburetor adjustments.

• Always wear safety glasses or goggles when starting and running your engine.

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• Always keep your fuel in a safe place away from sparks, heat or anything that can ignite.

• Always ensure the aircraft is secure and will not move once the engine is started.

• Always rebind your transmitter to your receiver(s) after setup and before rst ight.

• Always ensure the throttle failsafe is set to low throttle in your transmitter.

• Always perform a range check prior to ight.

• Always cut off the fuel supply (pinch or disconnect the fuel line to the carburetor) or use

the throttle linkage to shut off the air in order to stop the engine.

• Never use hands, ngers, or any other body part to stop the propeller.

• Never throw any object into a propeller to stop it.

• Never run the engine in the vicinity of loose small objects, such as gravel or sand, to avoid

the propeller uncontrollably throwing such materials.

• Never wear loose clothing or a loose neckstrap when operating your model engine as these

items could become entangled in the propeller.

• Never have loose objects such as screwdrivers, pencils, etc. in your pockets when operating

your model engine. These could fall into the propeller.

• Never allow fuel to come into contact with eyes or mouth. Gasoline and other fuels used
in model engines are poisonous.

• Always ensure gasoline and fuel are stored in a clearly marked container away from
the reach of children.

Precautionary Guidelines

• Always mount the engine securely on a bench mount or high-quality engine mount.

• Always use the correct size and pitch of propeller for your engine. Refer to the Propeller Chart

in this manual.

• Always conrm proper balance of your propeller prior to installation of the engine. Failure
to do so could result in damage to the engine and/or airframe.

• Always utilize an electric starter to start your engine.

• Always discard any propeller that is nicked, scratched, cracked or damaged in any way.

• Always run your model engine in a well-ventilated area. Model engines can produce possibly

harmful carbon monoxide fumes.

• Always store your fuel safely in a sealed, water-resistant container.

• Always store fuel in a cool, dry location. Do not allow fuel containers to come in direct

contact with concrete, as the fuel may absorb moisture.

• Always responsibly discard fuel if there is condensation and/or water inside the fuel
container.

• Never return unused fuel from the fuel tank back into the fuel container.

• Never attempt to repair or modify a propeller beyond its intended use.

• Never handle model engines, mufers and/or tuned pipes until they have had time to cool.

They can become extremely hot when in use.

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Introduction

Congratulations on your purchase of one of the exciting new engines in the Evolution® small
block gas engine series. All of the Evolution brand gas engines are designed from the start to
provide you with excellent performance at a fraction of your previous operating costs. We have
painstakingly designed and tested each engine to ensure a hassle-free experience without giv­ing away anything in expected performance or durability. This manual, when read and followed,
will guide you through the simple steps to your success. Welcome to the Evolution family.

Small Block Gas Engine Design

Starting with our already proven glow engines enjoyed by thousands around the world, we en­deavored to take that excitement and experience into the realm of gasoline fuel to provide you
with a complete package; great performance and low cost of operation.

Step 1 Start with a great engine. The Evolution glow engines have provided thousands of users

excellent performance.

Step 2 Design a new carburetor system that will be reliable and provide for hassle-free use by

the owners. This new carburetor, with already proven technology, was modified to fit in
the available space in front of the cylinder and the unique needs of a gasoline fueled
engine. Built on to the front of the carburetor is a crankcase pressure-driven regulator
system. This system takes fuel from a muffler pressurized tank and meters it properly in
all attitudes of flight. A new cat’s eye style fuel metering system was added to allow for
more controllability to the low and mid-range throttle positions.

Step 3 Design the proper muffler system to handle the extra heat and expansion of the burnt

gas mixture when compared to a glow system. These changes included adding volume to

the muffler, and enlarging the outlet of the muffler to minimize backpressure while still
providing noise reduction.

Step 4 Design operating accessories that enhance the user experience. During our extensive

2 1/2-year testing program, we discovered a lot of new techniques and obstacles that are
unique to gasoline fueled small block engines.

• Because the amount of fuel consumed is one third that of a comparable sized

glow engine, the construction and reliability of the fuel delivery system to the
carburetor becomes three times as critical. Microscopic pieces of dirt that used
to safely pass through the larger fuel passages of a glow carburetor will wreak
havoc on a gasoline system. By using a quality inline filter like our Inline Filter

(EVOA105) we can take care of the dirt problem. One of these is included with

your engine.

• The same holds true for air bubbles from the tank or any small leak in the fuel

tubing; what would pass harmlessly through a glow carburetor simply is not tol­erated in a gasoline system because the air bubbles are effectively three times
the size they used to be. We have developed and sourced an excellent felt filter
clunk that, when used in the tank, stops all the air bubbles from moving into the
fuel delivery tubes. This felt clunk is critical to successful and reliable operation.
One of these is included with your engine.

• We found that high mufer temperatures would destroy normal Tygon® tubing
(the go-to choice for gasoline engines) within minutes. We found that Neoprene

tubing could withstand the temperatures, tended to degrade quickly in use. We

sourced the proper sized uoroelastomer (FKM) tubing (Gasoline Fuel Tubing
EVOA104), which withstands not only the high temperatures, but its durability

is much greater than that of either Tygon or Neoprene. The added bonus is that
it fits and holds well to the fuel fittings without any need for additional wire or
tie-wrap keepers. We have included a supply of this tubing with your engine.

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Included Content

ENGINE

• Mufer (EVOG20601)

• Mufer Screws & Gasket (EVO110E100A)

• Spark Plug (EVOG10350)

• Evolution/Spektrum™ Telemetry RPM
adapter cable (EVOA107)

• Med Gas Fuel Tubing (EVOA104)

• In-Line Fuel Filter (EVOA105)

• In-tank Felt Filter/Clunk (EVOA106)

Spark Plug

Fuel Nipple
High-Speed

Needle

OPTIONAL ITEMS

• Tachometer (HAN156)

• Propeller 15 x 6 (EVO15060) for break-in;
16 x 6 (EVO16060) for normal ight

• Optical Electronic Ignition Kill Switch
(EVOA100)

• Evolution Synthetic 2-Cycle Oil, (EVOX1001Q)

• Ultra Fuel Pump (HAN155)

Muffler

Low-Speed

Needle

Throttle

Arm

Installing the Engine

1. Secure the engine mount on the airplane
firewall. Tighten the engine mount screws
in the firewall.

2. Install the engine on the engine mount
according to the airplane manufacturer’s
instructions.

WARNING: Tighten all engine
mounting screws before each flight. If

you do not tighten the engine

mounting screws, the screws may
vibrate loose and cause the engine to
separate from the fuselage.

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Installing the Muffler

The muffler mounting accessory package
includes mounting screws (2), lock washers
(2), muffler gaskets (2) and L- wrenches (3).

Connecting the Throttle Linkage

1. Use a secure method to attach the
throttle linkage to the throttle arm on the
carburetor.

2. Power on the transmitter and receiver.

3. Move the throttle stick to the middle stick

position.

4. Adjust the throttle arm so the arm is 90

degrees to the throttle pushrod.

5. Center the throttle servo. Install a servo arm
with a hole 11mm (7/16 in) from the center

of the arm.

6. Use a clevis to attach the throttle linkage to

the servo arm.

Aftermarket muffler (BIS05610) shown.

Not included.

1. Put a lock washer on each of the muffler
screws. Push the muffler screws through
the muffler.

2. Align the muffler gasket with the exhaust
opening and the muffler mounting screws.

3. Tighten the mufer screws.

IMPORTANT: Tighten the muffler screws after

five tanks of fuel. The muffler screws may

loosen from heat and vibration.

After the third tightening, no further muffler

loosening should occur.

11mm

1.5mm

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Adjusting the Throttle Opening

1. Lower the throttle and center the throttle

trim.

2. Adjust the length of the throttle linkage
until the throttle is open 1mm.

3. Move the throttle stick up to conrm the

throttle opens. If the throttle does not
open, reverse the throttle channel in your
transmitter.

Attaching the Fuel Lines

Fuel Line

1. Connect medium diameter fluoroelastomer
tubing fuel line to the carburetor and the
fuel tank supply line.

4. Move the throttle stick and throttle trim
down to confirm the throttle closes.

5. If you reversed the throttle channel in your

transmitter and you are using a 2.4GHz
radio system, you must re-bind your radio
system to set the correct failsafe position.

2. Connect medium diameter FKM fuel line

to the muffler pressure nipple and the fuel
tank vent line.

RECOMMENDED PROPELLERS
15 x 6–17 x 8 (16 x 6 has tested to be the

best performer with this engine, although
the performance is very good throughout the

recommended range)

Attaching the Propeller and Spinner

1. Remove the prop nut and prop washer from
the crankshaft.

2. Install the spinner backplate, followed by
the propeller, prop washer and prop nut.

3. Cover the propeller with a cloth and use an

adjustable wrench to tighten the prop nut.

4. Install the spinner cone. Make sure the

5. Tighten the spinner screw(s) to secure the

spinner cone is not touching the propeller.
Trim the propeller opening if necessary.

spinner cone.

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Connecting the Electronic Ignition

The Evolution Electronic Ignition Assembly is designed and engineered specifically for the
small block engine series. It is smaller and lighter so it fits into tighter spaces of the airplanes

the engines are designed to power. The battery voltage required is between 4.8V (4-cell Ni-MH
pack) and 8.4V (2S Li-Po battery) and no voltage regulators are needed with any of these
batteries. We recommend a 2S Li-Fe battery (such as the Team Orion® Avionics Li-Fe Receiver
Pack 1300mAh 6.6V (ORI60503)) and we have done extensive testing with these packs. The
maximum amp draw at full throttle is 450mAh, and our more typical average has been between
250–300mAh.

The assembly consists of:

• Ignition module with battery connector, ignition sensor connector, tachometer readout
connector and spark plug connector

• Ignition sensor (already attached to your engine)

• Sensor magnet (already installed in the prop drive hub of your engine)

Mounting Your Electronic Ignition

• You can mount the unit in any orientation

and place that is convenient for your
installation. The module is sized to con­veniently fit into the tank compartment of
most glow powered airplanes alongside or
underneath the recommended fuel tanks.

You can also mount it to the rewall or

under the engine firewall extension if your

airplane is so equipped. Keep in mind that

it should be mounted away from the heat of
the muffler.

• Secure the ignition module to your chosen

location with foam padding to provide
vibration isolation. We typically mount it
conveniently with tie wraps after wrapping
the ignition in lightweight 1/4-inch foam
rubber.

• You may need to route both the spark plug

connector wire and the ignition sensor wire
through the firewall, so be sure to plan
ahead and provide adequately sized holes
that will allow you to pull either the ignition
sensor connector or the spark plug cap
connector through the holes for later
ignition removal.

• Mount a good quality radio receiver type

switch between the ignition unit and the
battery. Mount this switch in a convenient
place on the outer fuselage close to the
front of the airplane to make it easy to turn
the ignition on and off. Being able to easily
shut off the ignition is an important safety
consideration.

• For added security and controllability, add

an additional radio-operated kill switch

(such as the Optical Ignition Kill Switch
EVOA100) between the ignition battery con-

nector lead and the ON/OFF switch.

• Connect the ignition sensor wire to the

ignition module. The sensor wire will only
fit into one of the connectors so you cannot
connect it wrong.

• Connect the ON/OFF switch to the battery

connector lead of the ignition module. This
connector is the red connector.

• If desired, you can connect either the
separately available tachometer readout or
the included Evolution/Spektrum Telemetry

Adapter Cable (EVOA107) to the tachometer

readout connector. Plug the other end of
the adapter cable into your telemetry mod­ule’s rpm input port.

• Connect the spark plug connector to the

spark plug. This adapter has a push on and
rotate clockwise 1/8 turn locking
mechanism to ensure a solid connection.

Make sure you charge your ignition battery
and are now ready to operate your electronic
ignition with the engine.

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Fuel

This engine requires a mix of 20:1 gas to oil
lubricant ratio for break-in and a mix of 32:1

gas/oil ratio for normal operation in order to
last a long time.

The needle bearing at the bottom end of the
conrod depends upon this lube ratio to oper­ate properly.

Do not go higher than a 20:1 gas/oil ratio

for the first gallon of fuel. After this you may

decrease the oil content to a 32:1 gas/oil ratio
if desired. Do not go higher than a 32:1 gas/

oil ratio or the warranty on your engine will be
voided.

Fuel Delivery System

It is very important to properly construct
your fuel supply system to the engine to
avoid operating problems. Our experience has
shown that many seemingly engine related
operating problems are in fact fuel delivery
problems, not engine related
problems.

Fuel Filtering - Because of the incredibly small
amount of fuel that is being used by this

engine, ltration of the FKM fuel is mandatory

in three different spots in the system:

1. Between the fuel jug and the tank.

2. Within the fuel tank itself (with a ltered
clunk EVOA106).

3. Between the fuel tank and carburetor (with
an in-line fuel lter EVOA105).

Both of these lters (2 and 3) are included in

the engine package.
Tank Location - Because muffler pressure

is used to provide the pressurization to the
fuel regulating and metering carburetor, the
tank still needs to be mounted in line with
the carburetor, and as close to the rear of the
engine as possible. Care taken in mounting
the tank as described will provide trouble free
operations in all flight attitudes.

Tank Choice and Construction – Choose a

tank between 8–14 oz (240–420 mL). These
tanks will yield 12 minutes (for the smaller
tank) to 25 minutes (for the larger tank) of full

throttle flying time.

To properly mix the fuel, for a mix of 20:1 gas
to oil, add 6.75 oz of good quality 2-stroke
oil to one gallon (or 53 mL of oil to one liter)
of 87–93 octane fuel. (EVOX1001Q Evolution
2-stroke oil is recommended) We prefer to

add the oil first to our fuel container and to
add the gasoline second. This helps to ensure
a good mixture of the oil with the fuel at the
outset.

We have tested our own Evolution 2-stroke oil,

Valvoline, Shell, RedLine and Husqvarna oils.

Other quality 2-stroke oils should work as
well. Do not use Amsoil synthetic oil in
any form.

• Ensure you use a tank stopper made for

use with gasoline and/or smoke oil.

• We suggest a three-line tank system; one

for the line to the carburetor with the clunk
attached internally, one for the muffler
pressure to the tank, and one dedicated
to fueling/defueling the tank. We try to
avoid the T-fittings and other inline valves
because they can be a possible source of
air/fuel leaks.

Gasoline-resistant
Rubber Cap

Fuel Tank

Filtered Weight

Vent Tube

Fueling Tube

Gasoline-resistant Tube

Carb Nipple

Fuel Filter

Gasoline-resistant Tube

• Ensure you use the provided FKM tubing in

all the plumbing of the tank, externally and
internally.

• Ensure you use the included felt lter clunk

inside the fuel tank.

• Ensure you use the included inline lter

between the tank and the carburetor.

• Ensure there is a good seal system for
the dedicated fueling/defueling line. We

highly recommend the HAN116 Fuel Filler

Assembly for its sleek look and ease of use
when installed on your airplane.

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Engine Break-in

Your new engine needs to be broken-in to ensure a long life of all the components. This engine

features a piston ring design, which requires a specific break-in procedure to ensure a tight seal
between the piston ring and liner. For this to be accomplished, this process requires repeated
heating and cooling cycles, and must be done at a needle setting that is slightly rich of peak to
ensure the ring expands and contracts. The ring needs to “grow” into the liner for it to develop a
good seal.

Breaking in the piston ring and liner by running it too rich does not provide the necessary parts
growth to accomplish the needed piston ring and liner fitting. However, using too lean of a
setting will cause the ring to become damaged by overheating. Please follow the steps below to
ensure a successful experience.

Important considerations during break-in

• Perform the break-in process with the

engine mounted on your airplane. There is
no need to bench-run the engine prior to
mounting it on your airplane.

• Use the suggested break-in prop to begin

your break-in process. This provides a light
load and high rpm that, when matched
with the heat of the engine, will break in
the engine properly.

• Use the proper recommended fuel with a
20:1 gas to oil ratio for the rst gallon of

operation.

The proper break-in flight procedure is to fly
the airplane at full throttle through a series

of gure eight maneuvers (i.e. Cuban Eight).

These maneuvers in particular benefit the en­gine because, when climbing, the additional
load on the engine will increase the tempera­ture and, when diving, the lighter load and
higher rpm will decrease the temperature,
thus providing the heating/cooling cycles
required for the break-in process.

Break-in process

• Firsttankoffuel: Set the high-speed

needle valve at 1.50 turns out and use the

suggested break-in prop. Run the engine
on the ground for its first tank of fuel and
DO NOT go above half throttle. Cycle the
throttle between idle and half throttle every
minute.

• Second tank of fuel: Tune the needle valve
to be slightly rich of the peak RPM at full
throttle without a drop in RPM. Do not run
at full throttle on the ground for more than

30 seconds at a time. Tune the low speed

needle valve for a smooth transition from
idle to mid-range, go back to full throttle
to confirm the main needle valve setting
and then fly. During this flight, be sure to
be conscientous of extended periods of
heating the engine. Be sure to mix-in some
cool-down dives and lower-throttle flying.

• Third tank of fuel: Fly the engine at a high
throttle while performing the recommended
figure eight maneuvers. This will help the
piston ring and cylinder liner to expand and
contract; helping the breaking-in process.
Tune the needle valve to be slightly rich of
the peak RPM as necessary.

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• Fourth tank of fuel: Select one of the rec-

ommended propellers for normal operation
and mount it on your engine. Tune the main
needle valve to be slightly rich of the peak
RPM and the low speed needle valve for a
smooth transition from idle to full throttle
and continue to break-in the engine in
flight.

Do not worry about an engine setting being
slightly rich during this process. When set
correctly, the engine will occasionally sound

as if it is misring (which it is). During the

climbing maneuvers this should go away and
might return during the diving maneuvers. If it
does not go away during the climbs, land the
airplane and lean the high-speed needle by

1–2 clicks, then take off and y again. Enjoy

the break-in process—you are doing a lot of
flying.

Continue to fly the airplane through the first
gallon of fuel and then change the fuel mix-

ture to 32:1 for continued operation.

Telemetry

Telemetry is a huge asset to help you tune
your engine. The ignition module is even
capable of communicating with Spektrum
telemetry systems directly so you won’t have

to add an additional RPM sensor. You will

need to connect the Evolution Ignition

Telemetry Adapter (EVOA107) between the

RPM port on the ignition unit and the RPM
port on your Spektrum telemetry module in
order to utilize this feature. Telemetry systems
other than Spektrum may require a dedicated
RPM sensor.

We recommend using the Spektrum DSMX Full
Range Aircraft Telemetry Module (SPM9548)

in conjunction with the included adapter. This
system allows you to see real-time RPM and
temperature readings from the engine.

The temperature sensor should be wrapped
around the base of the spark plug on the
cylinder head. Using telemetry gives you an
accurate representation of actual temperature
and rpm figures during use, and warnings
can be set to go off if your engine is getting
too hot.

The temperature range can be 275–300ºF

on average. Set your maximum temperature

warning to go off if the engine exceeds 350ºF.

If your engine is continually near this peak
temperature or higher, immediately decrease
throttle to bring the temperature down. If this
continues to occur, land the airplane and add
additional baffling to your cowl. It is not good
for the engine to run at temperatures this high
and could cause damage if not attended to.

Starting and Operating the 20GX Engine

Now that you have the baseline needle valve
settings, you are ready to start your engine for
the rst time. With the 20GX it is very
important to allow the temperature to

stabilize above 170°F (75°C) before making

any adjustments; adjusting prior to the engine
warming up will lead you to inaccurate
settings. As the engine warms up you will
notice the rpms naturally rising.

If you do not have a temp gun or have sensors
installed on your engine, allow the engine to
run at half throttle for at least 45 seconds be­fore attempting to set the high-speed needle.
If you have accurately set the low-speed
needle as described you should not need to
adjust it.

Priming

1. Make sure your ignition is off.

2. Open the throttle fully and, either by hold­ing a finger over the carburetor intake or

the mufer exhaust, ip the propeller 6

times.

3. Remove your nger from either the carbure­tor or muffler exhaust and flip the engine

another 6 times.

4. Close the carburetor completely with your
throttle stick and then open it two detents
from closed. This will allow the engine to
start at a high throttle setting.

Because each fuel system and installation
is slightly different, you may find the need
to modify the above procedure for your
individual setup. The above procedure should
work for most installations.

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Starting and Running the Engine

Until the engine is broken in, use an electric
starter to start the engine. Once it is fully
broken in it can be started by hand, but it is
easier and safer to start the engine with an
electric starter.

1. Turn on the ignition.

2. Rotate the propeller in a backwards direc­tion against compression.

3. Push the starter rmly against the nose

cone and engage. The engine should start

relatively quickly, within 1–2 seconds. Once

the engine starts disengage the starter.

4. Let the engine run at mid-throttle for 45

seconds to stabilize the temperatures.

a. If the engine doesn’t start quickly, disen-

gage the starter. Continuously running
the starter can flood the engine.

b. Check to make that fuel is moving

through the carburetor system.

c. If the engine appears not to have any

fuel, repeat the priming procedure
above.

d. Repeat 1–4 of Starting and Running the

Engine.

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High-Speed Needle Adjustment

Because of the small amount of fuel actually
needed for this engine, needle adjustments
need to be made in small increments. It may

take 5 seconds or more before you will notice

a running change in your engine after making
it. Be patient. Use a tachometer, this is a very

important part of properly setting your high­speed needle valve.

The procedure below is for ground setting the
needles prior to flight. The final adjustments
need to be made after noting the performance
in the air.

1. With engine started and warmed up, open

the throttle fully and note the rpm. Listen to

the engine.
a. If the engine occasionally mis-fires but

maintains a fairly constant rpm after 5

seconds, your engine is rich. Reduce the

throttle to idle and turn in (clockwise)

the high-speed needle 2 clicks. Repeat
this until the engine stops mis-firing.

b. If the engine does not mis-fire and the

rpm steadily decreases from the highest
rpm achieved when you opened the
throttle, it is lean. Reduce the throttle

to idle and open (counterclockwise)

the high-speed needle 2 clicks. Repeat
this until the engine maintains the rpm
achieved when the throttle is wide open
Your goal here is to achieve a good
transition between high and low speed,
and that the high-speed rpm will be
steady on the ground.

2. Fly your aircraft for the in-air testing.
a. During flight, if the engine seems to slow

down or sag when climbing, your engine
is running slightly lean. Land the
airplane and open the high-speed
needle valve 2 clicks and take-off again.

b. During flight, if you hear the engine mis-

firing occasionally in level flight, this is

an indication it is running too rich. Land

the airplane and close the high-speed
needle valve 2 clicks and take-off again.

c. Repeat the above process until your

engine performance is steady and
repeatable. This high-speed needle
setting should not change more than

+/– 1–2 clicks in the future when using

the same propeller. If it does, something
is wrong in the fuel delivery system and
should be investigated.

If you are using onboard telemetry and have
a temperature monitor on the head of your
engine, your readings should be between

200°F (93°C) and 300°F (149°C). If you see
consistent temperatures above 340°F (171°C)

you should land your airplane and add
baffling to your cowl in order to increase
cooling to the engine. See the Telemetry
section for information on the proper
positioning of your sensor.

12

Low-Speed Needle Adjustment

If you have properly set the idle need, the

low-speed setting should be within 1/16th of

a turn from perfect. Remember we are talking
about minute amounts of fuel going through
the carburetor, any adjustments you now
make to the idle needle should be very, very
small.

Take into consideration the length in service

(e.g. break-in time) and the size of propeller

you are using. In the beginning, use a smaller

propeller early in the break-in process. You

will not be able to achieve an idle much below

2000 rpm. The larger the propeller, the lower

your idle rpm will be, and the more broken in
your engine is will allow a lower idle rpm

(14 x 6 should be about 1800–2000 rpm).
Your engine will idle at low-speed needle set-

tings from far to0 rich to far too lean without

any damage, so the quality of the idle is not
a good indicator of the proper low-speed
needle settings. The transition from idle to full
throttle will be used to determine the position
of the low-speed needle.

1. With the engine started and warmed up,
open the throttle fully then reduce to idle

and note the rpm. Listen to the engine.

2. Let the engine idle for ten seconds and

then rapidly advance the throttle to full
open. One of three things will occur:

a. The engine responds instantaneously.

Your low speed needle is set perfectly.

Now use your throttle trim to achieve the
lowest reliable idle.

b. The engine slowly accelerates to full

throttle. This indicates the low speed
needle is set two rich and that fuel is
building up in the crankcase. Shut the

engine off and lean (clockwise turn)

the low speed idle screw by an amount
equal to the thickness of the screwdriver
blade you are using to make the adjust­ment. Restart the engine and repeat
steps 1 and 2.

EN

c. The engine stutters or stops on it way to

full throttle. This indicates the low speed
needle is set too lean. With the engine

off, richen (counterclockwise turn) the

low speed idle screw by an amount
equal to the thickness of the screwdriver
blade you are using to make the
adjustment. Restart the engine and
repeat steps 1 and 2.

3. Once you have achieved the instantaneous

throttle transition, your low-speed needle is
set perfectly. Now go back and recheck your
high-speed needle valve setting. There is
some interaction between the two needles

so you might need to do this process (HS
and LS needle setting) a couple of times.

Patience here will reward you with an easy
to use engine. Don’t try to do this too
quickly.

4. Once you have achieved the instantaneous
throttle transition your low speed needle
is set perfectly. It is possible that with a
heavier-loaded propeller that you may need
to richen the needle in order to attain a
smooth, instantaneous response again, but
using the above procedure should lead you
to the proper setting everytime.

13

EN

20GX Evolution Engines Specications

Displacement Bore Stroke Weight Cylinder Propeller

20cc 30.5mm 27.9mm 24.9 oz Ringed 16 x 6 @ 8,850 rpm

Weight

Engine Only 24.9 oz
Muffler 5.2 oz
Ignition 3.5 oz
Total 33.6 oz

E = Height*

F = Length

G = Crankshaft thread size
H = Muffler bolt spacing

B A

F

H

G

C D

Dimensions (mm)

* Height is from engine C/L to top of cylinder head.

A B C D E* F G H

46 58 25 67 90 108 5/16 x 24 36.5

Troubleshooting Guide

If the Engine Does Not Start

• Check and use a new spark plug if needed.

• Check fuel lines.

• Check for proper mechanical function by

turning the engine over.

• Check that the carburetor is correctly

installed.

• Check that the mufer pressure line is
attached and free from any bends or
blockages.

Mechanical Faults

If the engine cannot be turned over easily

• The most likely cause is the engine is

flooded and by turning the engine over you
are trying to compress the fuel, not air.

1. Remove the spark plug.

2. Cover the cylinder head with a cloth or

paper towel and turn the propeller over
to expel all the excess fuel.

3. Replace the spark plug and try starting

again.

• A possible cause is the piston in the

cylinder is seized: loosen and unscrew the
cylinder head bolts.

1. Carefully remove the cylinder liner.

2. Visually examine the piston and cylinder

to find the possible cause of the engine’s
mechanical problem.

Mechanical repairs must ALWAYS be

completed by an authorized Horizon Hobby
service center.

Maintenance

After each flying session:

1. Fully drain the fuel from the tank.

2. Start the engine and run it until the fuel is
completely run out of the engine.

3. Try starting the engine three more times or

until it will no longer fire. This gets all the
fuel out of the engine.

If you need additional help or have any
questions, please call Horizon’s Support
Team. Horizon has trained technicians
who are qualified to answer your engine
questions.

14

Exploded View

EN

23

22

12

28

3

18

20

30

29

36

43

21

19

30

20

8

17 15

16

30, 31

34

32, 35

26

4, 30

5

6

7

9

14

13 12 11 10

25

26, 32, 35
35

26
43

33

24

26

37423826414039

15

EN

Parts List

# Description Part

1 Cylinder Screw (6) EVO120123
2 Spark Plug EVOG10350
3 Cylinder Head EVOG20103
4 Cylinder Head Gasket (2) EVO120112

5 Cylinder EVOG20202
6 Piston Ring EVO120236
7 Ringed Piston EVOG20214R
8 Piston Pin & Retainer EVO120213
9 Connecting Rod EVOG20204
10 Prop Washer & Nut EVO100228

11 Drive Washer EVOG20219
12 Spacer Washer EVO91225
13 Front Bearing EVO91109
14 Crankcase EVOG20101

15 Rear Bearing EVO400110
16 Drive Key EVO91218
17 Crankshaft EVOG20210
18 Back Cover Set EVOG20102
19 Back Cover Screw EVO61122
20 Muffler Assembly EVOG20601

21 Complete Ignition System EVOG10300
22 In line Fuel Filter EVOA105
23 In Tank Fuel Filter/Clunk EVOA106

# Description Part

24 Carburetor Assembly EVOG15801
25 Ignition Sensor Set EVOG10310A
26 Carburetor Gasket Set EVOG15108A
27 Carb Mount Gasket Set EVOG61816A
28 Medium Gas-FKM Fuel

Tubing

29 Muffler Mounting Screw

Set

30 Gasket Set EVO120416
31 Muffler Gasket Set EVO100609
32 High-Speed Needle EVOG15829
33 Carb Regulator Screws EVOG12123
34 Carburetor Retainer EVO61119
35 High-Speed Needle

Valve Assmbely
36 Fuel Nipple EVO100114
37 Regulator Case Parts EVOG1087A
38 Carb Barrel Spring EVOG10814
39 Throttle Arm EVO46866
40 Throttle Barrel EVOG15813

41 Low-Speed Adjustment EVOG15844
42 Main Carb Body EVOG15827

43 Carb Barrel Retaining Bolt EVOG46825

EVOA102

EVO110E100A

EVOG15812

2-YEAR LIMITED WARRANTY
What this Warranty Covers - Horizon Hobby, Inc.,

(Horizon) warrants to the original purchaser that
the product purchased (the “Product”) will be free

from defects in materials and workmanship for a
period of 2 years from the date of purchase.
What is Not Covered - This warranty is not trans-

ferable and does not cover (i) cosmetic dam­age, (ii) damage due to acts of God, accident,

misuse, abuse, negligence, commercial use, or
due to improper use, installation, operation or

maintenance, (iii) modication of or to any part
of the Product, (iv) attempted service by any-

one other than a Horizon Hobby authorized ser-

vice center, (v) Product not purchased from an
authorized Horizon dealer, or (vi) Product not

compliant with applicable technical regulations.

OTHER THAN THE EXPRESS WARRANTY ABOVE,
HORIZON MAKES NO OTHER WARRANTY OR REP-

16

RESENTATION, AND HEREBY DISCLAIMS ANY AND
ALL IMPLIED WARRANTIES, INCLUDING, WITHOUT
LIMITATION, THE IMPLIED WARRANTIES OF NON­INFRINGEMENT, MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE. THE PURCHASER
ACKNOWLEDGES THAT THEY ALONE HAVE DETER­MINED THAT THE PRODUCT WILL SUITABLY MEET
THE REQUIREMENTS OF THE PURCHASER’S INTEND-

ED USE.
Purchaser’s Remedy - Horizon’s sole obligation
and purchaser’s sole and exclusive remedy shall be

that Horizon will, at its option, either (i) service, or
(ii) replace, any Product determined by Horizon to

be defective. Horizon reserves the right to inspect

any and all Product(s) involved in a warranty claim.

Service or replacement decisions are at the sole
discretion of Horizon. Proof of purchase is required

for all warranty claims. SERVICE OR REPLACEMENT
AS PROVIDED UNDER THIS WARRANTY IS THE PUR-

EN

CHASER’S SOLE AND EXCLUSIVE REMEDY.
Limitation of Liability - HORIZON SHALL NOT BE
LIABLE FOR SPECIAL, INDIRECT, INCIDENTAL OR
CONSEQUENTIAL DAMAGES, LOSS OF PROFITS OR
PRODUCTION OR COMMERCIAL LOSS IN ANY WAY,
REGARDLESS OF WHETHER SUCH CLAIM IS BASED
IN CONTRACT, WARRANTY, TORT, NEGLIGENCE,
STRICT LIABILITY OR ANY OTHER THEORY OF LI­ABILITY, EVEN IF HORIZON HAS BEEN ADVISED OF
THE POSSIBILITY OF SUCH DAMAGES. Further, in

no event shall the liability of Horizon exceed the
individual price of the Product on which liability
is asserted. As Horizon has no control over use,
setup, final assembly, modification or misuse, no
liability shall be assumed nor accepted for any re­sulting damage or injury. By the act of use, setup
or assembly, the user accepts all resulting liability.
If you as the purchaser or user are not prepared to
accept the liability associated with the use of the
Product, purchaser is advised to return the Product
immediately in new and unused condition to the
place of purchase.
Law - These terms are governed by Illinois law

(without regard to conict of law principals). This

warranty gives you specific legal rights, and you
may also have other rights which vary from state
to state. Horizon reserves the right to change or
modify this warranty at any time without notice.

WARRANTY SERVICES
Questions, Assistance, and Services - Your local

hobby store and/or place of purchase cannot
provide warranty support or service. Once
assembly, setup or use of the Product has been
started, you must contact your local distributor
or Horizon directly. This will enable Horizon to
better answer your questions and service you in
the event that you may need any assistance. For
questions or assistance, please visit our website
at www.horizonhobby.com, submit a Product
Support Inquiry, or call the toll free telephone
number referenced in the Warranty and Ser­vice Contact Information section to speak with a
Product Support representative.
Inspection or Services - If this Product needs to
be inspected or serviced and is compliant in the
country you live and use the Product in, please use
the Horizon Online Service Request submission
process found on our website or call Horizon to

obtain a Return Merchandise Authorization (RMA)

number. Pack the Product securely using a ship­ping carton. Please note that original boxes may
be included, but are not designed to withstand the
rigors of shipping without additional protection.
Ship via a carrier that provides tracking and insur­ance for lost or damaged parcels, as Horizon is not
responsible for merchandise until it arrives and is

accepted at our facility. An Online Service Request
is available at http://www.horizonhobby.com/
content/_service-center_render-service-center. If
you do not have internet access, please contact
Horizon Product Support to obtain a RMA number
along with instructions for submitting your product
for service. When calling Horizon, you will be asked
to provide your complete name, street address,
email address and phone number where you can
be reached during business hours. When sending
product into Horizon, please include your RMA
number, a list of the included items, and a brief
summary of the problem. A copy of your original
sales receipt must be included for warranty con­sideration. Be sure your name, address, and RMA
number are clearly written on the outside of the
shipping carton.

NOTICE: Do not ship LiPo batteries to Horizon. If
you have any issue with a LiPo battery, please
contact the appropriate Horizon Product Support
office.
Warranty Requirements - For Warranty consider­ation, you must include your original sales receipt
verifying the proof-of-purchase date. Provided war-

ranty conditions have been met, your Product will
be serviced or replaced free of charge. Service or
replacement decisions are at the sole discretion of
Horizon.

Non-Warranty Service - Should your service not
be covered by warranty, service will be completed
and payment will be required without notification
or estimate of the expense unless the expense
exceeds 50% of the retail purchase cost. By sub-

mitting the item for service you are agreeing to pay­ment of the service without notification. Service
estimates are available upon request. You must in­clude this request with your item submitted for ser­vice. Non-warranty service estimates will be billed
a minimum of ½ hour of labor. In addition you will
be billed for return freight. Horizon accepts money
orders and cashier’s checks, as well as Visa, Mas­terCard, American Express, and Discover cards. By
submitting any item to Horizon for service, you are
agreeing to Horizon’s Terms and Conditions found
on our website http://www.horizonhobby.com/
content/_service-center_render-service-center.

ATTENTION: Horizon service is limited to Product
compliant in the country of use and ownership.
If received, a non-compliant Product will not be
serviced. Further, the sender will be responsible
for arranging return shipment of the un-serviced
Product, through a carrier of the sender’s choice
and at the sender’s expense. Horizon will hold
non-compliant Product for a period of 60 days from
notification, after which it will be discarded.

17

EN

WARRANTY AND SERVICE CONTACT INFORMATION

Country of

Purchase

United States of

America

United Kingdom

Germany

France

China

COMPLIANCE INFORMATION FOR
THE EUROPEAN UNION

Declaration of Conformity

(in accordance with ISO/IEC 17050-1)

No. HH2013032703
Product(s): EVO 20cc (1.20) Gas Engine
Item Number(s): EVOE20GX

The object of declaration described above is in
conformity with the requirements of the
specifications listed below, following the provi-

sions of the European EMC Directive 2004/108/

EC:

EN55022:2010 + AC:2011
EN55024:2010

Signed for and on behalf of:
Horizon Hobby, Inc.

Champaign, IL USA
March 27, 2013

18

Horizon Hobby Contact Information Address

Horizon Service

Center

(Repairs and

Repair Requests)

Horizon Product

Support

(Product Technical

Assistance)

Sales

Service/Parts/

Sales:

Horizon Hobby

Limited

Horizon Tech-

nischer Service
Sales: Horizon

Hobby GmbH

Service/Parts/

Sales:

Horizon Hobby

SAS

Service/Parts/

Sales:

Horizon Hobby –

China

Steven A. Hall

Executive Vice President and Chief Operating Ofcer

International Operations and Risk Management
Horizon Hobby, Inc.

servicecenter.horizonhobby.

com/RequestForm/

www.quickbase.com/db/

bghj7ey8c?a=GenNewRecord

888-959-2305

[e-mail]

888-959-2305

[e-mail] Units 1–4 , Ployters Rd,

[phone]

[e-mail]

[phone]

[e-mail]

[phone]

[e-mail]

[phone]

Instructions for disposal of WEEE by
users in the European Union

This product must not be disposed of
with other waste. Instead, it is the user’s respon­sibility to dispose of their waste equipment by
handing it over to a designated collections point
for the recycling of waste electrical and elec­tronic equipment. The separate collection and
recycling of your waste equipment at the time of
disposal will help to conserve natural resources
and ensure that it is recycled in a manner that
protects human health and the environment.
For more information about where you can drop
off your waste equipment for recycling, please
contact your local city office, your household
waste disposal service or where you purchased
the product.

4105 Fieldstone Rd

Champaign, Illinois,

61822 USA

Staple Tye

Harlow, Essex, CM18 7NS,

United Kingdom

Christian-Junge-Straße 1

25337 Elmshorn, Germany

11 Rue Georges Charpak

77127 Lieusaint, France

Room 506, No. 97 Chang-

shou Rd.

Shanghai, China 200060

2013 Horizon Hobby, Inc.

©
Evolution and the Horizon Hobby logo are registered trademarks of Horizon Hobby, Inc.

The Spektrum trademark is used with permission of Bachmann Industries, Inc.
Tygon® is a registered trademark of Saint-Gobain Performance Plastics Corporation.

All other trademarks, service marks and logos are the property of their respective owners.

Created 03/2013 32913