SAITO FG-21 Gasoline Engine Instruction Manual

: June 3, 2024
: SAITO

Table of Contents

Specifications
Fuel
Ignition
Propeller
Break-in MOST IMPORTANT!!
Adjustment of carburetor after initial break-in.
Tappet adjustment
Documents / Resources

FG-21 Gasoline Engine
Instruction Manual

Specifications

Bore| 032.0mm| Stroke| 26.0mm| Disp. 20.9cc| Weight (Approx.)| Body: 690g / Muffler: 83g / Ignition system: 100g / Engine mount: 156g
---|---|---|---|---|---|---
Applications| 4-stroke glow 100-110 class| RPM Range Approx. 2,000-9,500rpm| Max on ground| Approx. 8,000-9,00Orpm
Propeller| 15″x8″-16″x6″| Plug| SP-1 or SP-2| Battery for ignition system| Voltage:6-12V greater than 1,000mA *
Standard accessories| •Engine mount set
•Hexagonal wrench
•Ignition system(w/sensor)| l set
1 set
1 set| • Limit gauge (0.1t) for tappet adjustment
•Spanner for tappet adjusting lock nut
•Spark plug[SP-2](Attached to the engine)| 1pc
1 pc
1 pc| •Plug wrench
•Muffler set
•Anti-loosening nut| 1pc 1 set 1 pc
Optional parts| •Filter with weight [G36-154] •Tappet adjusting kit [30-161]| •Durable tube for Gasoline (1 m) [G36-155] •Digital tachometer [G17-167]| •Aluminum spinner nut [100-30]

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

Fuel

The fuel is mixture of regular gasoline or high-octane gasoline and high-quality 2-stroke engine oil.
[Example of oil recommendation]
Klotz KL-200 Original Techniplate
Deluxe Materials PowerModel 2T-S
ENEOS RACING SPEC PRO-2T (SAITO STANDARD) etc.
If such oils are not available in your country, then please ask the oﬃcial SAITO distributor in your country for an alternative.
NEVER use “cheap oil” designed for utility engines for brush cutter, lawn mower, or chain saw 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.

Ignition

● Ignition arrangement- Place the main unit as far from other electrical devices as possible.

Plug cord (meshed high tension cord)
Insert the plug cap of the plug cord deeply into the plug attached to the cylinder to make sure it will not come oﬀ.
Sensor cord
Connect with the cord from the sensor attached to the engine.
Battery cord (black / red cord)
Use a fully charged battery that has adequate spec. (6-12V, more than 1000mA is recommended). Between the battery and main unit, make sure to set a heavy duty switch whose capacity is higher than 3A.
Tachometer cord
Connect the digital tachometer (Option). Otherwise the connector is normally vacant.

Propeller

Recommended propeller is APC15x8~16×6 which brings approx.9,000rpm. Larger size or greater pitch can cause engine broken due to overload.
Use a well-balanced one. Never use the propeller that has been scratched or damaged even if slightly.
As the propeller is compressed slightly, tighten the propeller nut every hour of operation.

Break-in MOST IMPORTANT!!

Prop-recommendation : APC16”x 6”.
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.
Check that the slow needle is set to the reference position. (Depth 0.9~1.1mm from the surface of the throttle lever. )
Before starting the engine, open the main needle Approx. 1+1/2 turns from fully closed.
Start the engine (using a starter is recommended for safety).
Soon after starting, Open throttle gradually up to full. In the meantime turn the main needle CCW.
Continue to turn the main needle CCW until the RPM declines (to approx 4-5,000rpm) keeping the throttle opened fully.
Run in this very rich condition for 1 liter of fuel.
Now “initial” break-in is done.

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+1/3~1+1/2 turns CCW from fully closed
Slow needle ：Approx. 2+1/2~3 turns CW (Approx. 0.9~1.1mm) from the surface of the throttle lever. (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 return 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.
Turn the slow needle CCW slightly if the engine hesitates for a moment or stalls before the engine reaches max RPM because the mixture is too lean.
Turn the slow needle CW slightly if the engine is slow to reach peak RPM (full throttle set) because the mixture is too rich.
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 approx. 60～90 degrees 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.

Tappet adjustment

The valve clearance should be checked and adjusted after Break-in and every after 2 hours while the engine is cold. Before adjusting tappet gaps, tighten the screws around cylinder etc.

Remove the spark plug and rocker arm covers from the cylinder. Then turn the prop CCW by hand to place the piston at TDC of compression stroke.
Loosen the lock nut and adjust the gap by hexagonal wrench until you get the correct gap (below pic) for both of intake & exhaust.
Once the gap is set, tighten the lock nut and attach the plug and covers.
Turn the prop by hand to check if the compression is enough. If the gap is less than 0, the valve is always opened sightly and lose compression.
Then adjust again.

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 pray 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 stand 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.

SAITO FG-21 Gasoline Engine - FIG6 SAITO FG-21
Gasoline Engine - FIG7

SAITO FG-21 Parts List

No.	Description	Qty
1	Cylinder	1
6	Piston	1
7	Piston pin	1
8	Piston pin retainer	2
9	Piston ring	1
10	Connecting rod	1
14	Cylinder screw set	1 set

14-1,-2
15| Crankcase| 1
17| Rear cover (Back plate)| 1
19| Breather nipple| 1
20| Front ball bearing| 1
22| Rear ball bearing| 1
23| Crankshaft| 1
27| Tpaer collet& Drive flange| lea.
27-1,-2
28| Prop washer & Nut| lea.
28-1,-2
31| Crankcase screw set| 1 Set
31-1,-2,-3
32| Engine gasket set| 1 set
32-1,-2,-3,4,-5,-6,-8
33| Cam gear housing| 1
35| Cam gear| 1
36A| Cam gear shaft| 1
37| Steel washer set| 1 Set
38| Tappet| 2
39| Pushrod| 2
40| Pushrod cover & Rubber seal| 2ea.
40-1,-2,-3
41| Rocker arm| 2
42| Rocker arm screw & Nut| 2ea.
42-1,-2
43| Rocker arm pin| 2
46| Valve set (In & Ex)| 1 set
---|---|---
46-1;2
47| Valve spring & Keeper & Retainer| 2ea.
47-1,-2,48
48| Valve retainer| 2
49| Rocker arm cover| 2
69| Intake pipe| 1
74| Muffler| 1
75| Muffler manifold set| 1 set
75-1,80
80| Muffler nut| 2
82-1| Carburetor compete| 1 set
82-1-1,-1-2,-1-3,-1-4,-1-5,-1-7,-1-8,-1-9,
-1-13,-1-14,-1-15,-1-16,-1-17,-1-18,-1-19,
-1-20,-1-21,-1-22,-1-23,-1-24,-1-251-1-26,
-1-27,-1-28,32-5,85,8813,89,90-1,91-1
85| Full throttle needle| 1
87| Throttle barrel assembly| 1 set
82-1-5,-1-9,888,89
888| Throttle lever| 1
88B,90-1
89| Idle needle| 1
90| Carburetor screw & spring set| 1 set
82-1-7,-1-8,-1-13,-1-16,-1-26,-1-28,90-1
91| Carburetor gasket set| 1 set
32-4,-5,-6,82-1-9,-1-14,-1-18,-1-20,-1-22,-91-1
95| Engine mount set| 1 set
95-1,-2,-3,-4,-5,-6
110| Anti loosening nut| 1
152| Screw-pin (to fix drive flange)| 1
153| Electronic ignition system| 1 set
153-1,-2,-3,-4,-5
160| Pump assembly| 1 set
82-1-17,-1-18,-1-19,-1-20,-1-21,-1-22,-1-23
-1-24,-1-25,-1-26

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: 047-378-4156
FAX: 047-378-4155