ngh GTT70 Horizontally Opposed Twin Cylinder 2 Stroke RC Gasoline Engine Instruction Manual
- June 10, 2024
- NGH
Table of Contents
GTT70 Horizontally Opposed Twin Cylinder 2 Stroke RC Gasoline Engine
Product Information
The NGH GTT70 is a horizontally-opposed twin-cylinder 2-stroke gasoline engine designed for use on a model radio control airplane. It has a bore of 37.3mm, stroke of 32mm, and volume of 69.9cc (2×34.95cc). The carburetor used is the Walbro WT978 and the spark plug type is CM6. It has a maximum output of 7.9 HP/8300rpm and an RPM range of 1600-8000rpm. The ignition is NGH automatic advancing angle ignition (RoHS and CE Certified Rcexl Manufactured) and requires DC 4.8V – 8.4V 1000mAH power. The engine weighs 2070g and the ignition weighs 180g. It is recommended to use 90# unleaded gasoline with fully synthetic lubricants (non-4-stroke lubricants) in a break-in fuel ratio of oil: lubrication = 35:1.
Product Usage
Before operating the product, it is important to read the instruction manual to become familiar with the features of the product. The GTT70 engine is a precision product that must be operated with caution and common sense and requires some basic mechanical ability. This product is not intended for use by children under 15 years of age without direct adult supervision. To set up the carburetor, close the choke before the first start of the engine and quickly rotate the propeller to suction fuel oil from the tank into the carburetor. When starting the engine, open the choke. The throttle control arm is an infinitely adjustable-speed device that controls the turning speed of the engine. Connect the oil tank to the engine through the fuel nozzle. It is important to remove fuel from the carburetor after flight to prevent rubber engine components from deteriorating over time, which can cause a loss of engine performance. To do this, start the engine without connecting the fuel pipe until all the fuel in the carburetor has been used up. It is important to follow all instructions and warnings in the manual prior to assembly, setup, or use to operate the product correctly and avoid damage or serious injury. Do not attempt disassembly, use with incompatible components, or augment the product in any way without the approval of the company. While using the product, ensure that no one is in front of or to the sides of the propeller when starting or running the engine to avoid injury. Also, be cautious while handling the engine and ignition components as they can cause burns and other personal injuries.
GTT70 Horizontally-opposed twin-Cylinder 2- Stroke RC Gasoline Engine
Dear customer:
Thank you for purchasing our new Horizontally-opposed twin-cylinder 2-Stroke
NGH GTT70 gasoline engine. Your new GTT70 engine has been developed by NGH
engineers to offer all hobbyists a new 2-Stroke engine. You will be delighted
with stability, fuel economy, plenty of power of your new GTT70 engine. We
hope that you will enjoy with your new engine, and have many fun and safe
flying experiences with its use.
Safety Instruction and WARNINGS!
Please read the 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.
GTT70 engine is NGH R&D manufacturing precision products. It must be operated
with caution and common sense and requires some basic mechanical ability. This
product is not intended for use by children without direct adult supervision.
Don’t attempt disassembly, use with incompatible components or augment product
in any way without the approval of our company. It is 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.
Age Recommendation: RC engine is not a toy! Not for children under 15
years.
The engine is designed for use on a model radio control airplane. If it is
used for any purpose, we cannot be responsible for its reliability of safety.
- NGH or their dealers aren’t responsible for any loss, injury or damage resulting from the miss-use of RC engine.
- Keep away from the rotating propeller area while operating the engine.
- Do not wear loose clothing near the engine or the propeller.
- Do not operate the engine near loose material such as dirt, gravel, ropes, sand, etc.
- Always run your model engine in a well-ventilated area. Model engines produce possibly harmful carbon monoxide fumes.
- Always ensure that the propeller is securely attached to the engine shaft and all retaining fasteners are tightened properly before each flight.
- Always stand clear of and behind the propeller, ensure the face and body are far away from the propeller blade after trajectory. Never allow anyone, to be in front of or to the sides of the propeller when starting or running the engine.
- Always ensure that small parts in the children can’t touch place to prevent children from swallowing parts;
- Always check the propeller nut tightening.
- Gasoline is extremely flammable. Be careful of any sparks from electrical contacts such as fuel pumps, battery charger, etc.
- Allow your engine stop and cool before touching or fueling. The running engine of the surface temperature is high, easy to cause burns and other personal injury.
- Be sure to check whether there are loose bolts before flying. When install a muffler, the muffler in the threads of the screw into the engine exhaust, until twist fixed, it is recommended to use screw glue (Such as LOCTITTE 242、243).
- Ensure the engine and muffler in aircraft fairing environment with cold air, make sure the engine cooling.
Product Specifications
Type: Horizontally-opposed twin-cylinder 2-Stroke AIR Cooled gasoline engine
( Only used for fixed-wing aircraft model）
Bore：37.3mm| Stroke：32mm
Volume：69.9cc ( 2×34.95cc )| Carburetor: Walbro WT978
Max Output：7.9 HP/8300rpm| RPM Range：1600-8000rpm
Ignition: NGH Automatic advancing angle ignition (RoHS and CE Certified: Rcexl
Manufactured)
Ignition Power: DC 4.8V – 8.4V 1000mAH| Spark plug type：CM6
Fuel：90# Unleaded gasoline + Fully synthetic lubricants (Non-4-stroke
lubricants)| Break-in fuel ratio: oil :Lubrication = 35:1
Recommended propeller：23×8-10, 24×8-10 (Two blades）| Weight: engine 2070g,
ignition 180g
Carburetor setup and adjustment:
NGH GTT70 horizontally-opposed twin-cylinder 2-stroke gasoline engine used
Walbro WT carburetor, it has the perfect stability of idle speed and
acceleration sensitivity.
Always remove fuel from the carburetor after flight. not doing so will result
in rubber engine components deteriorating over time, causing loss of engine
performance.
Methods: start the engine without connecting the fuel pipe until we run
out of fuel in the carburetor.
Setup Carburetor
As shown in figure
- Choke. Close it before the first start the engine, and quickly rotating propeller, the fuel oil suction within the tank into the carburetor, when you start the engine should be open it.
- The throttle control arm. Infinitely adjustable-speed device, control the turning speed of the engine.
- Into the nozzle. Connect the oil tank and supply the fuel to engine.
- High speed needle. After fully open the throttle control arm ②, adjust the high speed needle can get the best high speed.
- Idling speed needle. Put ② return to the initial position, adjust the idling speed needle can obtain satisfactory low speed.
- Idle mixture adjustment screw. Adjusting the fuel and air mixing ratio at idle, it actually control the initial position of ②, adjust ⑥ and ⑤ will obtain the better idling speed.
The factory setting status:
- ④ —High speed needle. Fully closed (clockwise) before exiting(anticlockwise) 1.5-1.75 times；
- ⑤ —Idle speed needle. Fully closed (clockwise) before exiting(anticlockwise) 1.5-1.75 times；
- ⑥ —Idle mixture adjustment screw. The throttle control arm at the other end of the limit pawl near the screw cone about 1mm.
The initial setup of the engine is factory settings, the engine first start don’t need to adjust.
Adjust Carburetor:
When the engine running, you want to adjust the carburetor, please adjust it
based on factory settings:
In the process of adjusting the carburetor, please use a high-quality
tachometer to determine your adjusted results, the tachometer you need to buy
one.
First adjust the high speed needle: engine run time will be turned on at full
throttle position, adjust the high needle and watch the change of the
tachometer, make the engine rpm reach the max per minute. engine work in a
stable high speed (Please note: Do not let the engine run boundary for a long
time, this is a big damage for engine).
Adjust the idle speed needle: the throttle return to the idle position, adjust
the idle needle and watch the change of the tachometer. let the engine run in
a stable state of idle speed (advice 23 * 10 wooden double blade propeller
idle speed at 1300rpm). when necessary and idle mixture adjustment screw joint
adjustments to ensure the engine idle speed stability, smooth acceleration; if
the engine is idling difficult to start (exclude CDI ignition power shortage,
excessive fuel combustion chamber, spark plug problems and so on). this shows
that air-fuel ratio (A / F) is low at idling, please adjust idle mixture
adjustment screw, increase air ratio. or adjust idle needle to reduce the
amount of fuel, A / F ratio to achieve appropriate proportion. (Tip: The
larger engine propeller, the more perfect lower idle speed you will get.)
When the engine high speed and idle speed adjustment is completed, try to run
the engine acceleration performance. first let the engine to run 10s at idling
and the quickly move the throttle control arm at full throttle position, there
will be the following three situations:
- A. Engine speed is responsive and smooth transition to the highest speed, instructions for the adjustment of the engine is very good.
- B. Engine acceleration has a cough performance, gradually transition to the highest speed. Illustrate the idle oil needle set relatively rich oil, the idle needle to make a small adjustment (clockwise rotation), and then try again, try to accelerate the reaction constant adjustment until the engine reaches your request.
- C. Rapid throttle when the engine suddenly stopped running, this shows that the idle needle set relatively lean oil, the idle needle to make a small adjustment (anticlockwise rotation), and then try again, try to accelerate the reaction constant adjustment until the engine reaches your request.
The Fuel Tank Connecting
CDI igniter connection
Starting the engine:
According the engine connection method, install the engine on RC airplane and
lock propellers. ensure that installed on the back of RC planes of firewall is
used metal flat washer or ratchet nut to prevent bolt in plywood.
- Made the carburetor initial setup and connect the spark plug, electronic ignition and sensors, put the fuel into the oil tank, connect the power and radio control equipment.
- Will power off the electronic igniter at this time, make the carburetor inlet port in a fully closed position. rapidly rotating propeller engine make the fuel in the tank inhalation of carburetor, please pay attention to the suction of fuel should not be too much, otherwise will drown the spark plug, the engine start difficult.
- Please open the carburetor throttle air inlet, power on the electronic igniter, then start the engine using the motor starter(or start bar), the engine will begin to work, the fans will adjust the carburetor according to your own need. according to the above steps you can adjust the carburetor adjustment.
Warning: Make sure all bystanders, especially children, at least 30 feet away from rotating engine.
Engine Break-in:
Please use the high quality synthetic oils, gasoline and machine oil’s mixing
ratio is 35:1.
NGH is recommended to use smaller size propellers at first break-in and
follow-up about 10 times in flight. keep medium speed running for 15 minutes
(no more than 4000rpm) after started engine, then high speed running for 3
minutes, again medium speed running for 5 minutes, high speed running for 3
minutes, reciprocating 3-5 times complete break-in. breaking in engine
carefully will increase its life. please make sure the engine got the complete
break-in before you use the larger load propeller.
( Note: Not recommended to use 24 * 10 inches above the propeller )
Engine cooling:
If your engine is installed in the fairing, there must be air entering to cool
the engine and ensure enough air flowing in the faring.
Reference data: outlet area should be 3-5 times than the entrance area to
ensure adequate cooling.
Engine Failure Removal:
If the engine is difficult to start, idle speed and high speed unstable.
please check: whether the electric circuit and oil line of engine is trouble,
whether the engine leaks air, whether the electronic ignition works or its
power supply is adequate, whether the spark plug flame out. if necessary,
replace with a new spark plug.
Engine Maintenance:
To reduce the fuel consumption, extend engine’s life, please adjust the
engine’s highest speed and make engine run in the output maximum speed of 95%
once the gas pedal full opened. if the load is large (propeller’s diameter and
pitches are big), the fuel must be adequate. if the load is small, the speed
will be high while the fuel consumption will be less. please make sure to
empty the carburetor after each flight, otherwise it’ll cause the rubber of
fuel pump aging to affect the engine performance. please clean the carbon
deposition on the spark plug and keep the gap from 0.7mm to 0.8mm between the
electrodes. if it’s difficult to start the engine, idle speed unstable or when
high speed operation flameout, please replace the spark plugs; please clean
the engine surface after used each time, it can make the engine get better
cooling. the carburetor may be blocked seriously if you use different brands
or types of lubricating oil together, you need select a better fuel filter. if
the engine low speed work for a long time, can lead to spark plug carbon
deposition; regularly check the fuel system, make sure do not leak fuel, do
not leak air.
Engine Guarantee:
If the NGH engine has performance defects caused by the defects of process,
material and manufacturing, we certify that: change for free within one year
and guarantee within two years since the date you purchased. please note the
guarantee is only for the original purchaser, not including: normal wear for
engine; damage caused by the failure of maintenance; damage for engine over
speed operation caused by using small propeller; bearing rust; crash; use
inappropriate fuel; damage caused by foreign bodies; damage caused by
unreasonable installation or operating environment; damage caused by improper
dismantle; damage caused by any modification.
Engine Break-in:
Please use the high quality synthetic oils, gasoline and machine oil’s mixing
ratio is 35:1.
NGH is recommended to use smaller size propellers at first break-in and
follow-up about 10 times in flight. keep medium speed running for 15 minutes
(no more than 4000rpm) after started engine, then high speed running for 3
minutes, again medium speed running for 5 minutes, high speed running for 3
minutes, reciprocating 3-5 times complete break-in. breaking in engine
carefully will increase its life. please make sure the engine got the complete
break-in before you use the larger load propeller.
( Note: Not recommended to use 24 * 10 inches above the propeller )
Engine cooling:
If your engine is installed in the fairing, there must be air entering to cool
the engine and ensure enough air flowing in the faring.
Reference data: outlet area should be 3-5 times than the entrance area to
ensure adequate cooling.
Engine Failure Removal:
If the engine is difficult to start, idle speed and high speed unstable.
please check: whether the electric circuit and oil line of engine is trouble,
whether the engine leaks air, whether the electronic ignition works or its
power supply is adequate, whether the spark plug flame out. if necessary,
replace with a new spark plug.
Engine Maintenance:
To reduce the fuel consumption, extend engine’s life, please adjust the
engine’s highest speed and make engine run in the output maximum speed of 95%
once the gas pedal full opened. if the load is large (propeller’s diameter and
pitches are big), the fuel must be adequate. if the load is small, the speed
will be high while the fuel consumption will be less. please make sure to
empty the carburetor after each flight, otherwise it’ll cause the rubber of
fuel pump aging to affect the engine performance. please clean the carbon
deposition on the spark plug and keep the gap from 0.7mm to 0.8mm between the
electrodes. if it’s difficult to start the engine, idle speed unstable or when
high speed operation flameout, please replace the spark plugs; please clean
the engine surface after used each time, it can make the engine get better
cooling. the carburetor may be blocked seriously if you use different brands
or types of lubricating oil together, you need select a better fuel filter. if
the engine low speed work for a long time, can lead to spark plug carbon
deposition; regularly check the fuel system, make sure do not leak fuel, do
not leak air.
Engine Guarantee:
If the NGH engine has performance defects caused by the defects of process,
material and manufacturing, we certify that: change for free within one year
and guarantee within two years since the date you purchased. please note the
guarantee is only for the original purchaser, not including: normal wear for
engine; damage caused by the failure of maintenance; damage for engine over
speed operation caused by using small propeller; bearing rust; crash; use
inappropriate fuel; damage caused by foreign bodies; damage caused by
unreasonable installation or operating environment; damage caused by improper
dismantle; damage caused by any modification.
Web: www.nghengine.com
E-mail: ngh@ncdmoly.com
Skype: blue-sky-tan
References
- IMI-HOBBY-MODELÁRSTVO-MODELSPORT-MODELLBOLT-SLOVAKIA-NITRA
- Changsha Guanghua Aviation Technology Co., Ltd._Electronic electrician
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