Φ29.0mm
22.0mm
72.7cc
22” x 10” 〜 23” x 10”
Bore
Main body : 2,600g / Muffler : 280g / Ignition : 380g
Stroke
Disp
.
Weight (Approx.)
RPM Range
Approx.
1,200-7,800rpmMax on ground Approx.6,200~7,500 rpm
Propeller
1/4-32 SP-1 or
SP-2 spark plug
Plug
Optional parts
2st-Gasoline 50㏄ class
Applications
Battery for ignition system
Voltage:6-8.4V, greater than 1,500mA
・Limit gauge (0.1t) for tappet adjustment 1pc
・Wrench for tappet adjusting lock nut
1pc
・Plug wrench
1pc
・Spark plug [SP-2](Attached to the engine)
5pcs
・Muffler set
1set
・Anti-loosening nut
1pc
・Ignition system(w/sensor)
1set
・Muffler lock tie
2pcs
・Hexagonal wrench 1.5mm
1pc
Specifications
FG-73R5 Instruction Manual
2. Ignition
●Place the main unit as far from other electrical devices as possible.
●Place the two switches of the ignition and the RC receiver as far from
each other as possible.
(1) Plug cord(meshed high tension cord)
Insert the plug cap of (1) Plug cord deeply onto the plug of #1 cylinder
to make sure it will not come off. The other caps and plugs should be
installed by the same way. (Refer to cylinder # on the reverse side)
(2) Sensor cord
Connect with the cord from the sensor attached to the engine.
(3) Battery cord (black / red cord)
Use a fully charged battery that has adequate spec. (6-8.4V, more than
1500mA is recommended). Between the battery and main unit, make
sure to install a heavy duty switch whose capacity is higher than 3A.
(4) Tachometer cord (optional)
Connect the digital tachometer (Option) to the main unit. Otherwise the connector is normally vacant.
Standard
accessories
Fuel Tank
Fuel Level
To Outside of the plane
Vent line
Fuel supply to carburetor
Fuel filler line
Vent line
Gasoline-compatible
tank stopper
Gasoline-compatible tubing
Filter with weight
Set the center of the carb
slightly above the fuel level
Close as possible
Hollow
out
Firewall
Approx.30mm
1. Fuel
●The fuel is a mixture of regular gasoline and high-quality 2-stroke engine oil.
●[Example of oil recommendation]
・ Klotz KL-200 Original Techniplate ・ Deluxe Materials PowerModel 2T-S etc.
●Be sure to use the mixture “gasoline : oil =15~20 : 1” by volume ratio. (Ex. 1000ml of gasoline should be mixed with more than 50ml of oil ).
●During the break-in process, use 15:1 mixed fuel to ensure the best lubrication for initial running.
●Any damage caused by the fuel used, in which the oil ratio is lower than 20:1 will not be covered by warranty.
●Do not use gasoline containing ethanol. It may cause not only power loss but also corrosion inside the engine.
・Filter with weight [G36-154]
・Rubber tube for gasoline(1m) [G36-155]
・Tappet adjusting kit [30-161]
・Digital tachometer [G17-167]
3. Propeller
●Recommended propeller is
Mejzlik D22”xP10” which brings approx. 7,100rpm.
●Use a reliable prop which brings maximum 6,500~7,500rpm in conformity to your plane.
●Use a well-balanced prop. Never use a prop that has been scratched or damaged even if slightly.
●Never use excessively light or heavy loaded prop. They may cause engine failure, big accident, or even injury.
●As the propeller is compressed slightly, tighten the propeller nut every hour of operation.
4. Break-in MOST IMPORTANT!!
●Before starting the engine, inject a suitable amount ( approx. 20〜30cc ) of engine oil into the lubrication nipple on the crankcase using a
syringe or pump while turning the propeller by hand. After that, plug this nipple. As excess is discharged from the breather nipple, attach a
tube to the breather nipple.
●Prop-recommendation for break-in process :
Mejzlik 22”x10”
●Use 15:1 fuel:oil ratio for break-in.
●Never make the fuel mixture lean during break-in. It could cause seizure even during idling or
low-speed running.
●Before starting the engine, open the main needle approx. 2 turns from fully closed.
●Start the engine (using a starter is recommended for safety).
●Run for 15~20 seconds at low speed to warm up.
●Open throttle gradually up to full. In the meantime turn the main needle CCW. Continue to turn the
main needle CCW to drop to 3,000~4,000rpm keeping the throttle opened fully.
●Run in this very rich condition for 1 liter or more of fuel.
●Now “initial” break-in is done.
ver. Sept, 2019
Switch Capacity :3A〜
Sensor
Battery
Voltage: 6-8.4V
Capacity : 1,500mA〜
Plug Cap
(2) Sensor cord
(
1) Plug Cord
Main Unit
(3) Battery Cord
(4) Tachometer Cord
Throttle
Full open
CCW to make
rich
Main
Needle
CW→Lean
CCW→Rich
CW→Lean
CCW→Rich
CCW→Rich
CW→Lean
Main needle
Slow (Idle) Needle
(Adjust with ⊖ screw driver)
Slow
High
Throttle lever
5. Adjustment of carburetor after initial break-in.
◇Needle reference position (Set after initial break-in)
●Start the engine after adjusting the needle to the following reference value.
●
Main needle：Approx. 1+1/2 turns CCW from fully closed
●
Slow needle：Approx. 7 turns CCW from fully closed
(Then throttle valve
should be fully closed)
●Actually, the best position of the needles vary depending on the prop,
temperature, humidity and so on. Please adjust as necessary after observing
the engine performance during flight.
◇
Peak adjustment
●After starting the engine, warm up for approx. 30 seconds at low speed.
●Achieve the peak at full throttle.
→Turn the main needle CW gradually to the position where the RPM is greatest (the peak). Continuing to turn the needle CW past the peak
could lead to seizure so turn it slowly and carefully. If the RPM suddenly decreases after passing the peak,
instantly turn the main needle
CCW
to again increase the RPM. Otherwise it could damage the engine seriously.
●Once achieving peak RPM, return the throttle to low speed. Make a note of the position of main needle at the peak at that time. ( How many
turns you did CW based on the reference value. )
◇
Slow needle Adjustment
●
After achieving peak RPM, next is slow needle adjustment. Open the throttle from low RPM to full throttle quickly.
●If the engine hesitates for a moment or stalls before the engine reaches max RPM, Itʼs because the mixture is too lean. Then turn the slow
needle CCW slightly.
●If the engine is slow to reach peak RPM (full throttle set), itʼs because the mixture is too rich. Then turn the slow needle CW slightly.
●Adjust the slow needle as above until the RPM follows the throttle movement smoothly. The important point is to adjust the slow needle
AFTER
the main needle has been adjusted to its peak.
●Now break-in at ground level is done. Adjust tappets by the method described later.
◇
Pre-flight / Flight adjustment
●
When the slow needle adjustment is done, check the response by revving up from low speed to full throttle quickly several times.
●Open the throttle fully and turn the main needle CCW 4~6 clicks from the peak position. This is to make the fuel mixture richer in the air
where the RPM get higher than on the ground.
●After all adjustments are made, fly your aircraft and fine tune the engine according to the situation. Basically tuning should be done with the
main needle. Readjustment of the slow needle is rarely needed if the first adjustment of the slow needle has been done successfully.
Correct Gap
Must not be inserted
Close to “0” with no limit
Limit gauge
(0.1mm)
Loosen the lock nut
Adjust the gap turning
the set screw
Top Dead Center
（The state both valves are closed)
Tighten the lock nut
to fix the set screw
6. Tappet adjustment
The valve clearance should be checked and adjusted after break-in and every time after two hours while the engine is cold. Before adjusting
tappet gaps, tighten the screws around cylinders etc.
1. Remove the spark plug and
rocker arm covers of #1
cylinder. Then turn the prop
CCW by hand to place the
piston at TDC of compres-
sion stroke.
2. Loosen the lock nut and
adjust the gap by hexago-
nal wrench until you get
the correct gap (below pic)
for both of intake &
exhaust.
3. Once the gap is set, tighten
the lock nut and attach the
plug and covers. Do the same
adjustment for the #3-#5-#2
-#4 cylinders in order.
4. Turn the prop by hand to check if
the compression is enough. If the
gap is less than 0, the valve is always
opened slightly and will lose
compression. Then adjust again.
SAITO SEISAKUSHO, CO., LTD.
www.saito-mfg.com
22-7, 3-chome, Tokagi, Ichikawa-shi, Chiba prefecture 272-0024, Japan Phone: 047-378-4156 FAX: 047-378-4155
All specifications and models are subject to change without notice.
Note:
●As it uses oil-mixed fuel, the plane may sometimes get dirty from the exhaust.
●Use a reliable and well-balanced prop. Otherwise it may cause an abnormal vibration and could result in a serious accident.
●During operation, all engine screws can loosen due to metal heat expansion. Check and tighten occasionally.
●When the exhaust valve gets dull by carbon or sludge especially in cold atmosphere, remove the rocker cover and apply some anti-rust
spray to the exhaust valve to help the valve to move smoothly.
●Pay attention to the surroundings so as not to disturb others by noise and exhaust.
●Always keep spectators behind the engine when operating the engine.
●As exhaust smoke is harmful, be careful not to breathe in or otherwise expose yourself to its harmful effects.
●Pay attention not to touch the rotating propeller when starting engine, and move to rear side of the aircraft once the engine is started.
●All responsibilities for the use of the engine, and other obligations and responsibilities based on laws, regulations, etc. are borne by the
purchaser and the user, and SAITO SEISAKUSHO CO., LTD. is exempt from any responsibilities.
Warranty:
●If there is any deficiency from the factory concerning manufacture, please consult with the shop or distributor you bought from. Our
company will be responsible for repair. However, any failure or trouble caused by unnecessary disassembly, modification, or other uses
than those provided in the instruction manual is not subject to warranty.
●Ignition system is subject to the warranty only for initial failure. Once the system has been activated successfully, it will no longer be subject
to warranty.
※
※If you use Li-Po, we recommend the spec less than 2,500mA capacity and
less than 30C discharge rate
