SAITO FA-91S Four-Stroke Glow Engine Instructions

SAITO FA-91S Four-Stroke Glow Engine

We would like to express our sincere thanks for your purchase of the SAITO FA -91S/91SGK engine, which is manufactured by Saito Seisakusho, Ltd. Please read our instructions carefully and treat your engine with care. Should there be a manufacturing defect, Saito Seisakusho, Ltd. will make necessary repairs at free of charge. You will notice a letter {A, A, C, etc.) stamped on the top of the right mounting lug. This identifies the production version of your engine. If you ever need to order a part or have a question about your engine, specify this letter along with the part number you need so we can better handle your request. This engine is designed and manufactured based on high efficiency and durability of the first AC method in the world.

AA C: Aluminum Piston, Aluminum Cylinder, Hard chrome Plated

Unique features of SAITO F A-91S/91SGK engines include:

• Cylinder-Thanks to the monolithic structure of cylinder head and cylinder with direct hard chrome plated inner surface without using cylinder liner, this engine emphasizes durability while it also offers lightweight and distortion-free structure with improved cooling efficiency.
• Piston-High silicon content aluminum is used in the piston construction. It also has a compression ring that increases the engine· efficiency.
• Crankshaft-Made of solid chrome molybdenum steel, and supported by two ball bearings.
• Combustion chamber- Increased combustion efficiency with improved hemispherical shape.
• Cam gear-Our front mounted cam gear design results in a compact engine.
• Cam-Features high-output type high cam.
• Carburetor-High-performance type with slow adjustment equipped.
• Propeller nut- Double nut design to prevent fall-off for safety.
• Exhaust sound-Real-plane-like exciting exhaust sound.
• Weight-Lightest in the class.

Explanation of 4 Stroke Cycle Engine

The four-stroke engine consists of four individual piston movements as illustrated above. ‘Stroke” means that the piston is moved from the upper dead center to the I ower dead center point. I n the four-stroke engine, one cycle is completed every two revolutions of the crankshaft.

1. Intake stroke
2. Compression stroke
3. Expansion stroke
4. Exhaust stroke

F A-91S/91SGK T ecbnical Data

B o r e

St roke v o l u m e

| 2 8.2 mm dia.                                               St rok e

14. 99 cc                                                W e i g h t

| 24.0  mm

  _,

Approx. 504g, engine only (Approx. 555 g w/muffer)

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Practical speed| Approx.2,000~11, 500rpm (Recormnended highest speed on ground: 9,000~11, 000  rpm)
Propeller (Standard)

Fu e l

| 12″X 9″~12″X!0″                                        Fuel flow 13″X 7″~13″X g•

1 4″X 6″~14″X 8″

Sxnthetic oil with 10~20% nitromethane content

| Approx. 37cc/minute (at full throttle, appox. 10,000 rpm)

Fuel flow varies depends upon propeller load. More fuel flow with larger load and less fuel flow with smaller load. (In actual flight, fuel flow somewhat increases.)

St atic t h r u s t| APC 13″X7″ – 2. 3kg Application APC 13″X8″ – 1. 8kg

APC 14″X6 ” – 2. 8kg

| Airplane of 2-cycle 45~60 class

RC Stunt Airplane, Scale Airplane, Sports Airplane CL Stunt Airplane

Accessories| Spanner for tappet adjusting screw         ······· 1 each ……. ……..

Tappet adjusting screw gap gauge (0. lt) ……. 1 each                  Main needle valve u.tension bar                                      1 each

Hexagonal spanner (wrench) (1. 5, 2.0, 2.5)                  1 each Muffler Set········································· l set

P-S glow plug (attached to the engine)……….. l each

Dimension

Fuel

It is very important for engines to use high-quality fuel containing 10 20% nitro. For consistent performance and long engine life, use fuel containing AT LEAST 20% lubricant by volume. (DO NOT USE LOW OIL FUEL) Since the 4-cycle engine has high exhaust temperature and carbon is apt to accumulate when caster oil type lubricants are used. The fuel filter is to be installed and SAITO F-1 is designed for this model engine.

Fuel tank

Please select the best fuel tank available in the market referring to the data for the capacity. Set the level of fuel in the tank to the height that is roughly the same ith that of inlet nipple of the carburetor. Also, put weight to the fuel inlet at a distance of approximately 35 mm from the rear wall of the tank. %Check for the crack in the aluminum pipe and silicon tube in the tank. Since the SAITO engine employs muffler pressure, careful attention is required for the leakage. Also, be careful not to make the length of piping silicon tube unnecessarily long. (Watch for possible crack.)

Plug
Since one explosion occurs in every two rotations in 4 stroke engine, selection of, the plug is critical. Use of improper plug results in trouble of engine. Since the performance of the engine varies according to the matching with the fuel or to the season, we recommend testing various types for the best performance. (Some plug type of the other manufacturer exhibits good match with SAITO engine. AIso, the performance of the plug deteriorates after many flight hours even if it is not broken, frequent exchange of the plug with new one would be necessary.)
Uee of SAITO SAI GPO1 S Gl Plag is recommended

Propeller

It varies according to the body of the airplane, however, standard size ranges froml2′ X9~12’X10″, 13″X7″13″ X9″, and 14′ XG14 X8 (as just a guideline). Please select the one available in the market with high reliability. (We recommend A PC.) Thorough balancing must be carried out. (Use a balancing device is recommended.)The  Use of unbalanced propeller creates excessive vibration, reduces performance and is dangerous. If you find flaws etc., replace it with a new one, as it is dangerous. Avoid operating the engine beyond 11, 000 rpm with light 1oad propeller on the ground and below 8, 500 rpm with a large load propeller otherwise crankshaft, bearings, connecting rods, cam gears, etc. may be damaged. L Use a propeller that matches to the airplane and turns in good condition in the range of 9, 000 to 10,500 rpm on the ground in view of the characteristics of this engine. (If propeller size is not in the standard, it is OK as long as the speed is within this range.) Speed varies depending upon the manufacturer and also, in some instances, it occurs with propellers in the same size those manufactured by the same manufacturer. We recommend testing various propellers.

Engine Mounting
Your engine can be mounted in any direction required. However, we recommend using the vertical or horizontal position if possible. An inverted engine may be damaged upon landing and requires that the glow plug be removed, with the prop turned over several times to remove any excess fuel, after each flying session. Use of SAITO Engine Mount is recommended To prevent loose engine mounting, the application of small quantity of rubber adhesive on the tip of M4 cap screw is effective.

Preparation before Staring Engine

1. The engine must be mounted to the sturdy test bench with correct parallelism or to the body of the airplane. (Engine must be firmly fixed in either case so that it does not move.)

2. For the break-in on the bench, use a fuel tank with a capacity between 400 and 500cc.

3. For the airplane body, use the one already installed. 3 For the fuel, use the one with approximately 15% nitro-content except for low oil content.

4. For the propeller, prepare AP C 13″X8″ propeller (around 9,900–10,00rpm at standard).

5. To fix the propeller, turn the drive flange in the forwarding direction (counterclockwise) and when pressure is felt, place the propeller in
   the horizontal position and fully tighten the double nut to fix. (Spinner must also be attached, as the starter will be used.)
   Caution: Additional tightening of the propeller must be made after every 10 flights. In particular, if you are using a wooden propeller, it would be compressed so that the nut can be easily 1oosened. Therefore, careful and thorough additional tightening is required.

6. Since a 4-stroke engine does not clearly exhibit peak conditions 1ike a 2-stroke engine, use a tachometer to prevent over-squeeze or overheating.

7. Attach silicon tube to the breather nipple to check the exhaust, of the breather (to check oil flow).

8. Muffler pressure must be used without fail. (Make sure that no leakage is occurring from the tank.)

9. Prepare necessary materials and tools for plug heat.

10. Prepare the starter and battery

Caution. If any spectator is watching nearby, please ask the one to move backward prior to starting the engine. A lso, the arm that. holds airplane must be kept away from the prop. When the engine is started, move to the back of the airplane. Any operation like needle adjustment must be carried out from the back of the airplane. If the airplane is not fixed, it is safe to ask your assistant to hold the airplane.

Engine Starting Method
The following procedure describes the condition in which the engine is mounted to the body of the airplane. starting method with a starter. (For your own safety, this method is recommended.

1. First, turn on the switch of the transmitter. Next, turn on the switch of the receiver unit to check throttle action and then, set
   throttle stick at the position fully closed.

2. Open the main needle by about 4 turns. (This is just a guide.)

3. Open throttle valve 1/4 to 1/3 from a fully closed position with the throttle stick. (Starting with an excessively opened throttle is
   dangerous as the airplane jumps forward.)

4. Turn the propeller in the reverse direction (clockwise) until the engine is compressed.

5. Power the plug8.

6. When the starter is activated. for about 5 seconds, the engine will start easily.

Caution: Do not start the engine with the starter at the position where the engine is compressed in a forwarding direction, at it is dangerous.

(B) Manual starting method (For safety, wear gloves and safety stick etc.)

1. First, turn on the switch of the transmitter. Next, turn on the switch of the receiver unit to check throttle action, and then, set the throttle stick at the position fully closed.
2. Open the main needle by about 4 turns. (This is just a guide.)
3. Set the throttle valve at full open with the throttle stick.
4. Close the exit of the muffler with your hand and then propel ler 2 to 3 turns forcibly in counterclockwise to choke.

Caution: Excessive fuel intake compresses the fuel and may damage connecting rod etc. Crank 1 to 2 turns with hand and check if no fuel compression has occurred. After the throttle valve is fully closed once with the throttle stick, open the throttle valve 1/4 to 1/3 with the throttle stick. (Starting with an excessively opened throttle is dangerous as the airplane jumps forward. ) Turn the propeller in the forwarding direction (counterclockwise) to feel compression (propeller in horizontal). Power the plug. After the plug is powered, wait for a few seconds, and, when the propeller is forcibly cranked in a clockwise direction, the engine starts in the forwarding direction by the explosion counteraction.

Caution: In the case of a 4-stroke engine. do not try to start the engine manually in a forwarding direction from the point where the engine is in compressed condition like in the case of a 2-stroke engine, as your finger may be injured due to the reverse action of the engine. The above starting method must be followed without fail.

Engine Break- In

As the break-in is an important procedure to pull out the maximum performance of the engine, it must be cautiously implemented.

1. After the fuel tank is filled up, start the engine as described in above.

2. After the opening of the throttle valve is set approximately 1/2 or less (just as a guide) with throttle stick, adjust engine speed to
   stabilized condition at approximately 6, 000 rpm or less in rich condition with main needle valve is opened 5 turns or more while carefully watching tachometer and exhaust oil density and discharge density from the breather. Run the engine in this condition for full tank fuel consumption. (Plug heated condition may also be employed if the case allows.
   Caution: Absolutely, never make fuel mixture to lean condition in the stage. Even if you drop the speed to the idling speed and run the engine at iow speed, seizure would occur if the mixture is lean. The object of this break-in is the initial familiarization of connecting rod, gears, moving parts and so on in the condition Mainly with rich fuel mixture

3. Next, set the throttle valve at full open and run the engine in rich condition for full tank. (In this stage, exhaust oil density and discharge density from the breather must also be checked.)

4. Then, run the engine at just before 9, 0009, 500 rpm for the half tank.

5. Finally, run the engine at peak speed and less speed alternatively and if the engine runs at peak speed without unevenness, a ground break-in has been completed for the time being. Then, after tappet clearance is adjusted according to the procedure described in Article J and the carburetor is also adjusted according to the following article, and after around 10 flights at less speed, break-in will be completed.

Caution for the flight: For early flights, fly airplane windward and keep a high altitude and distance so that the airplane is able to return to the airfield even if the engine has stopped. If you fly an airplane at a low altitude from the beginning, the body of the airplane may be damaged at an emergency landing due to engine trouble.

Handling and Adjustment of Carburetor
The basic steps for the adjustment of the carburetor are first obtaining peak speed (maximum speed) by adjusting the main needle and then, set idling speed (slow speed) using a throttle valve and slow needle. (Vice versa is not possible, however.)

1. After the fuel tank is filled up, start the engine as described in Article G. After the throttle valve opening is set at full open with throttle stick, cautiously obtain peak speed with the main needle while watching the tachometer and listening to the exhaust noise.
   Caution: Excessive closing of the main needle is very dangerous, as the propeller nut becomes loose. In such occasions, immediately
   turn the main needle in counterclockwise to loosen.

2. Next, slowly close the throttle valve and cautiously adjust the speed using a screwdriver for a slow needle and throttle stick for throttle valve opening so that the engine runs at an idling speed in the range of around 2, 000~2, 500 rpm in stable conditions. (See the figure below)

3. Once the idling speed is set, slowly open the throttle valve to full open. If the speed becomes irregular or suddenly increases in this process, carefully make fine adjustment with a slow needle so that the speed changes linearly from the idling to the peak speed.

4. When the above adjustment has been completed, quickly change the speed from idling to its peak. If the speed does not reach at its peak simultaneously with the c.ndition of the throttle valve fully opened, return the main needle by a single knurl notch. Then, quickly change the speed from idling to its peak, again. Repeat this procedure cautiously until you can obtain a good response

5. When all conditions are set, return the adjustment by 2 to 3 knurl notches (or about 300 rpm slower).
   Caution: When peak speed with full tank fuel is at 9,900 rpm, reduce speed by 300 rpm to set it at 9, 600 rpm. It is the key for longer service life to fun the engine at a speed slower than its peak by around 300 rpm and the bearingS WOuld hardly get rust.

   • Use standard values shown in the following figure as the standard for carburetor slow needle opening adjustment, though slight adjustment is required according to the engine mounting position, propeller type, fuel type, plug, weather condition, and so forth. For perfect adjustment, it is recomended to carry out fine adjustment while flying the plane and sounding out the positions of those best matched for each of slow, medium and high-speed.

Hints for Disassembly/Assembly Work
Disassembling and assembly ing of your engine are not recommended, however, follow the following instructions when necessary.

1. For the dismantling, put benchmarks on the parts by yourself (use a marking pen etc.) while checking the direction of parts in proper sequence. Also, clean each part. In particular, careful attention is required on the valve timing, valve inlet and exhaust, piston direction, connecting rod direction, and so forth.
2. The cylinder screws should be l00sened little by 1ittle in a crisscroSS pattern. If they are loosened improperly, you may distort the cylinder.
3. Assemble it with the same crisscross method, applying engine oil to the tips of the Screws. If you tighten the screws without oil, you may cause damage to the threaded areas.
4. Assemble the cam gear lining up the necessary marks per the diagram. The crankshaft should be positioned at the top dead center. Then the coincidence of the cam gear should be positioned below.
5. Position the piston, connecting rod, rocker arm, pins, push rod, tappet, etc., their original positions. Engine parts are mated after running and they must be returned to their original positions. When you do assemble your engine, apply engine oil to each part and reassemble them in proper sequence while carefully checking marks and directions without applying excessive.
6. ) Change in the mounting direction of the carburetor ( See figure)
7. Remove mounting cap screws so that the carburetor can be moved.
8. Turn the carburetor about 90 degrees as shown in Fisusing the section where the intake pipe is inserted into the cylinder as a fulcrum without removing carburetor and intake pipe.
9. Turn the carburetor in opposite direction at the previous position.
10. Return the carburetor to the mounting position and mount it with mounting cap screws. Careful attention is required for the tightening torque of cap screwS as excessive torque results in poor movement of the throttle valve.

All specifications and models are subject to change without notice.

SAITO SEISAKUSH0, GO. , LTD.

• 22-7,3-chome, Tokagi, I chkawa, Chiba 272-0024, Japan
• Phone 047-378-4156
• Fax
• 047-378-4155

32-1,32-2,32-3,32-4,32-5,32-6,32-7
338| Cam gear housing| 1
35A| Cam gear| 1
36A| Cam gear shaft| 1
37| Steel washer set| 1set
38| Tappet| 2
39| Pushrod| 2
40| Pushrod co v er & Rubber seal(40-1,40-2,40-3)| 2ea.
41| Rocker arm| 2

FA-91S

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| SAITO FA-91S Four-Stroke Glow Engine [pdf] Instructions
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