Saito FG-73R5 User Manual

FG-73R5 Instruction Manual

ver. Sept, 2019

Specifications

Bore

Φ29.0mm

Stroke

22.0mm

Disp.

72.7cc

Applications

2st-Gasoline 50 class

Weight (Approx.)

Mainbody : 2,600g / Mu er : 280g / Ignition : 380g

RPM Range

Approx.1,200-7,800rpmMax on ground

Approx.6,200~7,500 rpm

Propeller

22” x 10” 23” x 10”

Plug

1/4-32SP-1or

Battery for ignition system

Voltage:6-8.4V,greaterthan1,500mA

SP-2sparkplug

Standard

Limit gauge (0.1t) for tappet adjustment

1pc

Wrench for tappet adjusting lock nut

1pc

Plug wrench

1pc

Sparkplug[SP-2](Attachedtotheengine)

5pcs

Mu er set

1set

Anti-loosening nut

1pc

accessories

Ignition system(w/sensor)

1set

Mu er lock tie

2pcs

Hexagonal wrench 1.5mm

1pc

Optional parts

Filterwithweight[G36-154]

Rubbertubeforgasoline(1m)[G36-155]

Tappetadjustingkit[30-161]

Digitaltachometer[G17-167]

	If you use Li-Po, we recommend the spec less than 2,500mA capacity and
1. Fuel	less than 30C discharge rate

●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.

	Firewall			Vent line
		Fuel filler line
			Gasoline-compatible
		Vent line	tank stopper	Fuel Level
			Fuel Tank
		Set the center of the carb
		slightly above the fuel level
	Approx.30mm	Fuel supply to carburetor
		Gasoline-compatible tubing
Hollow
out			Filter with weight
		Close as possible		To Outside of the plane

2. Ignition
●Place the main unit as far from other electrical devices as possible.	Plug Cap	(1) Plug Cord
●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)			Main Unit
Insert the plug cap of (1) Plug cord deeply onto the plug of #1 cylinder			Sensor
to make sure it will not come o . The other caps and plugs should be
installed by the same way. (Refer to cylinder # on the reverse side)			(2) Sensor cord
(2) Sensor cord
Connect with the cord from the sensor attached to the engine.
(3) Battery cord (black / red cord)		(3) Battery Cord
Use a fully charged battery that has adequate spec. (6-8.4V, more than		(4) Tachometer Cord
1500mA is recommended). Between the battery and main unit, make			Battery
		SwitchCapacity:3A	Voltage: 6-8.4V
sure to install a heavy duty switch whose capacity is higher than 3A.			Capacity : 1,500mA
(4) Tachometer cord (optional)
Connect the digital tachometer (Option) to the main unit. Otherwise the connector is normally vacant.

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.

Throttle	Main
Full open	Needle

CCW to make

rich

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	Slow (Idle) Needle
●Main needle Approx. 1+1/2 turns CCW from fully closed	CW→Lean	(Adjust with screw driver)
●Slow needle Approx. 7 turns CCW from fully closed (Then throttle valve	CCW→Rich	CW→Lean
		CCW→Rich
should be fully closed)		Slow
●Actually, the best position of the needles vary depending on the prop,	CCW→Rich
temperature, humidity and so on. Please adjust as necessary after observing
the engine performance during flight.

Peak adjustment	CW→Lean	Throttle lever	High
●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, It’s 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), it’s 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.

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	2. Loosen the lock nut and	3. Once the gap is set, tighten	4. Turn the prop by hand to check if
rocker arm covers of #1	adjust the gap by hexago-	the lock nut and attach the	the compression is enough. If the
cylinder. Then turn the prop	nal wrench until you get	plug and covers. Do the same	gap is less than 0, the valve is always
CCW by hand to place the	the correct gap (below pic)	adjustment for the #3-#5-#2	opened slightly and will lose
piston at TDC of compres-	for both of intake &	-#4 cylinders in order.	compression. Then adjust again.
sion stroke.	exhaust.

	Top Dead Center	Loosen the lock nut	Adjust the gap turning	Tighten the lock nut
	The state both valves are closed)
			the set screw	to fix the set screw

Correct Gap

Close to “0” with no limit

Limit gauge

(0.1mm)

Must not be inserted

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 e ects.

●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.

All specifications and models are subject to change without notice.

SAITO SEISAKUSHO, CO., LTD. www.saito-mfg.com

22-7, 3-chome, Tokagi, Ichikawa-shi, Chiba prefecture 272-0024, Japan Phone: [phone] FAX: [phone]