Usage Guide for GRpro Gas Engines

DO NOT  Start The Engine Before Reading And Understanding The Safety Restrictions !!

Thank you for your purchasing a GRpro engine!  We Guarantee you the best gas engine with highest performance with the best price. The GRpro engine is specially designed for use on model aircraft with powerful torque output with very little weight. It is quite simple to get familiar its operation and adjustment. Moreover it is durable for powering your model providing hundreds of hours of stable high performance.

The best service life of the engine is about 300 hours. We recommend you keep track of the run time when using the engine..

Please make sure all the guidance in the User's Guide are fully read and understood before the first time you start the engine, especially the sections about safety and about the ignition system wiring.

Trial Operation or Run In

The trial operation is recommended to be performed before your first flight by installing the engine on the plane. And running at least one tank of fuel through the engine. Even though all engines are factory tested before delivery.

Lubricant and Fuel for Trial Operation It is recommended during this period to mix non-synthetic (petroleum base) lubricant into fuel in the ratio of 1:30.

Auchtung !!! Attention !!! Since the piston ring in the new engine is not perfectly associated with the cylinder chamber inner wall yet, adoption of synthetic lubricants in the trial phase will result in permanent damage to these parts and finally the engine will not be able to acquire the designed power output as the consequence.

The fuel used in the engine is recommended to be the standard lead-free gasoline with an octane level of 90/91. Gasoline with octane level higher than 90/91 however will not acquire higher power for this engine.

Installation Install the engine (especially the carburetor part) as much as possible in the engine cowl, so to acquire the best performance for the engine. Since if the carburetor protrudes out of the engine cowl, the unstable air flow may cause unsmooth engine operation or even engine failure in the air.

Engine Seat Processed screw holes are prepared on both sides of the back of the GRpro engine for fixing application. Please fix the engine with strengthened bolts, washers and nuts on the aircraft. The firewall should be made of aero composite (or other suitable materials) and fixed firmly on the aircraft. The thickness of the firewall is recommended to be at least 6mm thick for large gas engines.

Fuel Supply Line and Fuel Tank Please choose both the fuel tank and supply line designed for gasoline engines, and the outlet of the fuel tube and the fuel tank should be tied up tightly with wire as well as the connection the fuel tube with the clunk; also it has to be noticed that the clunk should oscillating freely in the fuel tank when the tank placed vertically without contacting the bottom. The inner size of the fuel tube should at least equal to the inner size of the fuel inlet port (or larger than).

Fuel It is recommended to use standard lead-free gasoline whose octane level at 90. Use of gasoline with octane level higher than 90/91 does not acquire higher power for this engine but may lower the rotating speed. So please use the recommended fuel. Lubricant After the run-in phase it is recommended to use SHELL two stroke race lubricant at 1:30 ratio. This way your GRpro engine will be kept clean during operation while the lubricant will provide excellent protection for the mechanical parts. High quality synthetic or mineral lubricant from other manufacturers can also be used on the GRpro engine only when they are designed for two stroke air cooled gasoline engines. In this case the ratio the lubricant be added should refer to respective manufacturer's advice.

Fuel Filter One or more high quality filter should be applied to prevent any impurities from entering the fuel tank. Special filters can be purchased from the model shop. Remember washing a new fuel tank with fuel several times before installing it on the plane for use, because any particles or impurities which are hard to detect with naked eyes would possibly block the precise tunnels inside the carburetor preventing proper operation and tuning of the engine.

Ignition System Please follow the wiring instructions of the ignition system carefully, and NEVER load the battery unless you are quite sure that the system is correctly connected. Starting the engine with incorrect system wiring will lead to ignition system damage. Damage due to such action will obtain no warranty from our company.

Carburetor/Mixing Proportion Base Principles: The engine requires correct fuel mixture with the air to operate correctly. The air intaking volume is controlled by the butterfly throttle.

If the engine does not supply proper power after starting, you can adjust the proportion screw on the carburettor to maximize the power output.

Low speed and High speed fuel mixture needles

The engine gets fuel from the low speed fuel mixture needle in any case, and starts to receive fuel from the high speed fuel mixture needle when the rotating speed rises to the mid range speed (2000—3000 rpm). When the engine operates in high Rpm almost all the fuel the engine receives is from the high speed injection needle (in proportion). The engine adjusting technique is just the configuration of the two injection needles which acquires correct air-fuel mixture for the engine under any rotating speed.

Lean Fuel means the fuel supplied by the carburetor is insufficient under certain butterfly changeover states. Engine operates in the insufficient fuel state (sufficient to operate) will have a higher rotating speed and a smoother rotation as well. However the engine will be the same it will run hotter (as the fuel proportion for taking away the heat is less).

Rich Fuel means the fuel supplied by the carburetor exceeds the actual need the engine operation demands under certain butterfly changeover states. The consequence is lead to the opposite way compared with that of Lean Fuel meanwhile the spark plug will not be able to work normally due to overwhelmed fuel (engine will shut off ).

Generally speaking the low speed injection needle should be configured a little Lean without interfering the normal operation when the engine shifts from idle speed to medium speed. The engine will be unstable or even shut off when boosted from idle speed to medium speed at the over-lean fuel state while oppositely at the over-rich fuel state the engine may in some case hesitation  when suddenly transitioned up from idle speed to high speed.

The high speed injection needle should be configured correctly namely the engine will operate at the highest speed without encountering any damage due to the heat from the operation under lean fuel state. While oppositely over-rich fuel state will also cause the irregular engine operation and the engine will not acquire desired rotating speed (power output)

There are two needles on the carburetor respectively marked “L” and “H”. the L one represents the idle speed (low speed) mixture needle while the H one stands for the high speed mixture needle. By turning these two needles clockwise the fuel mixed into the engine will be reduced to the lean fuel state, while the rich fuel state side can be attained by turning the needle counterclockwise.

In case the mixture needles have to be re-configured due to any reasons (such as disassembled for maintenance), it is recommended to turn the low speed mixture needle counter clock wise by two and a half turns and one turn for the high speed needle. (while paying attention not to over tighten the needle which may result in needle or carburetor damage)

Warning: DO NOT adjust the  butterfly without guidance since its design is special. Any improper adjustment may cause unstable engine operation or even permanent damage.

Warning: Please read carefully all the safety restrictions before any attempting to start the engine.

DO NOT start the engine without an assistant holding the plane.

Please check carefully the ignition system wiring again following the wiring instructions before starting the engine.

Always assume that the engine will start at any time, and be highly cautious of spinning propellers they are Dangerous

Preparation before starting the engine:

For the first time starting the engine, please turn the low speed needle counterclockwise by one and a half turn, and one turn counterclockwise for the high speed needle, so as to configure a start setting at which the engine will be able to operate in idle speed and under a rich fuel state under any valve position.

Fill the fuel tank full with fuel (attention: the fuel and lubricant proportion should be correctly adjusted), make sure the ignition switch is at OFF position  find a reliable assistant to hold the plane firmly.

Full open the air valve

Block the valve with thumb or forefinger and slowly rotate the propeller counterclockwise until fuel passing through the fuel line into the carburetor is confirmed. Then flip the propeller several times to make sure the fuel has entered the engine.

Close the air valve butterfly to 2-3mm open and prepare for start.

Make sure the ignition switch is at “ON” position.

Flip the propeller several times till it starts and repeat above procedures if it doesn't.

Starting the Engine

Adjusting the carburetor Adjust for the idle or medium speed Needle.

Warning: Do not adjust the engine during operation. All adjustment should be performed after the engine is shut off and the ignition switch is in the OFF position.

Please check the idle and acceleration performance after warming up the engine to operating temperature. The idle speed should be stabled between 1800~2000 rpm . If the idle speed can not stay reliable at 1800~2000 rpm due to a rich fuel state, please turn the low speed fuel mixture needle by one eighth  of a turn each time till the operation is smooth and once it goes smooth, please try opening the throttling by 1/3 (about 2500~3500 rpm). If the engine delays or shuts off, the idle speed may be over lean fuel which requires adjusting the idle speed needle by 1/16 of a turn. If the engine approaches to the medium speed after it delays, please turn the idle speed needle by 1/16 of a turn clockwise. Repeat above procedures till the idle speed is stable and clearly responding to medium or low speed acceleration.

Carburetor Configurations High Speed Needle

Warning: Do not adjust the engine during operation. All adjustment should be performed after the engine is shut off and the ignition switch is in the OFF position.

Once the low speed configuration is done, the high speed mixture needle should be adjusted. The configuration in principle is that slowly adjust to the correct mixing proportion from the full throttle and rich fuel state. Full open the throttle and turn the high speed injection needle till the engine operation is rough and unsmooth so to make sure the engine is running under a rich fuel state

Turn the high speed mixture needle by 1/8 of a turn each time and wait 5~10 secs after each adjustment. Make sure the working temperature is responding to the fuel needle adjustment. If during the 1/8 adjustment the rotating speed decreases then the adjustment will be over the limit. Please turn the high speed needle by 1/4 of a turn, make sure the rotating speed reaches the highest Rpm, this way the engine initial speed can be acquired and then turn back the needle to make sure it will not lean out with altitude.

Check the idle speed and medium speed acceleration performance. In case re-adjustment is needed, please adjust the high speed settings after the adjustment. Repeat above procedure till the engine operates smoothly.

Details of eletric ignition coil:

Red cable is the positive pole (+)

The electric ignition timing has already been set at the factory.

Correct electronic ignition timing is required for the normal operation of this engine.

Battery ：  4.8 V - 6 V

Troubleshooting

Case 1:

The engine operates normally on the ground however severe rich fuel situation appears when taking off or in the air.

Possible Causes: the positive pressure in the cowling or the carburetor port is impacted by the propeller slip stream.

Resolves:

1. install additional cowling in front of the carburetor to shield it from air flow

 2. install a inlet pipe / velocity intake to the Carburetor

Case 2:

 Sometimes rich sometimes lean mixture while in the air

Possible Causes: If the engine operates normally on the ground but turns out to be unstable in the air especially when the altitude changes, this is the most frequent situation when the carburetor protrudes out the cowling.

Resolves : 1. Install additional cowling in front of the carburetor

                     2. install a inlet pipe / velocity intake to the Carburetor

Case 3:

 The engine operates normally but gradually starts to run erratic

Possible Causes: The engine operates normally but gradually starts to run erratic, please check by following

Check the ignition battery: make sure the voltage and current is still within the normal range.

Check whether the ignition: system wiring is complete including the plug caps and the earth.

Check the spark plug: replace with new ones if it is dysfunctional.

Check the internal filter of the carburetor: Impurities accumulated in long term service will gradually block this filter which is extremely fine and precise.

Maintenance

It is recommended to drain the fuel tank after each days flying and always make sure to use fresh 90/91 Octane lead free gasoline.

If the engine will be stored for a long periods, please drain off the fuel tank and run the engine with the fuel line off so as to drain the carburetor of all fuel.

Check the spark plug regularly which should be mild brown. The milder the color is, the more it is closer to lean while the darker the more to rich.

Check the propeller, make sure it is locked tightly especially the wooden propellers as they may compress in the centre and become loose.