User Manual

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Note： During early stage of flights, take the height high enough to land safely in case the engine stop in the air suddenly. It
will reduce the risk of crash or landing accident.
12. Adjustment of carburetor
Before adjustment, please set both needles as the standard values.
In principle, the carburetor should first achieve peak by adjusting the main needle. Then performing idling with the throttle
valve and the slow needle. (Unless the peak is certainly achieved, idle adjustment will be difficult and not stabilized.)
(1) After filling up the fuel tank, start the engine as described in Chapter 10 and run it for 1 minutes in rich condition. Then fully
open the throttle valve with the throttle stick.
(2) By turning the main needle observing tachometer and exhaust sound, achieve peak carefully.
(3) Next, close the throttle valve until the engine runs stably with an idling rotation around 1,800rpm by adjusting the slow
needle with a (-) screw driver carefully. (During flight, its rather stable with slightly high adjusted at idling. )
*The best richness of the air-fuel mixture at slow speed is depend on the flight style. Generally, Scale flight requires stability in
low speed so slightly lean condition is preferable. On the other hand Acrobatic flight requires quick response from low
through high, so slightly rich condition is preferable.
(4)Once the idling is set, get the throttle valve fully opened gradually. If the revolution becomes slow or goes up suddenly,
adjust the slow needle carefully until rpm raises linearly from idling to peak by fine-tuning.
(5)After adjustment of (4) is completed, perform the process from idling to peak quickly. If revolution gets delayed to achieve
peak even if the throttle valve is fully opened, fine-tune the main needle and perform the same process. Repeat this
fine-tune and response check carefully until the response improves.
*Tip for adjustment of the slow needle is to make lean as possible as the engine dont get stole when open the throttle valve
quickly. At the same time, since a gas-engine has narrow range of air-fuel ratio, adjustment of the needles is stricter than a
glow-engine. And both needles are interfered slightly from each other so confirm the balance of peak and response after
adjustment.
*To keep the engine life longer, adjust the fuel mixture as rich as possible in the range it doesnt affect to the running. Carb
adjustment is affected by many factors such as prop, flight style, atmosphere (humidity, temperature, ...) ,oil, plug, fuel, and
so on. Please keep trying to find the best condition to match your plane.
Caution：Too much throttling the main needle is very dangerous because it might cause knocking and the prop nut might be came
off. Once you notice abnormal vibration or sound during throttling the main needle, just return to open the needle immediately.
13. Normal operation, maintenance, and additional information
(1) Just after start up the engine, perform warm up running in rich condition for about 1 minute, and just before stop run it at
idling for 1 minute to cool down as well. When stop the engine after the final flight of the day, be sure to stop by cutting the
fuel to remove fuel from the carburetor. And remove the fuel from the tank and reserve it with special care.
(2) Charge the battery for the ignition system and RC device fully. (Since the ignition system generates high tension, be careful
of electrical shock.)
(3) Lubrication for piston, connecting rod, bearing or cam gear is a blow-by lubrication in which the oil in the fuel goes into the
crankcase from the clearance between the cylinder and piston. Therefore the engine life is affected by the property of the
fuel oil. Please use reliable oil.
(4) Since over closing the main needle causes overheating, adjust a little more rich than peak. Over closing leads to knocking or
overheat and has an adverse effect on the connecting rod and cam gear. Where the airplane achieves peak completely at
the attitude of ascent should be a proper peak of the engine during flight.
(5) When connecting the exhaust pipe to the cylinder or attaching the prop nut, apply thin coat of silicon rubber (not exces-
sively) or adhesive on the thread section before tightening. This prevents leakage or loosening.
(6) Occasionally tighten the prop nut, exhaust nut, and whole screws.
(7) Take an extreme care for safety when operating the engine or flying the model airplane not to bother others.
(8) An engine for a model airplane is not a toy. Handle it with an extreme care.
(9) After completing ground break-in or operating the engine for 1 hour, adjust tappet gaps (valve clearances) by following
procedure to compensate initial wearing, while the engine is cold.
#1 cylinder should be adjusted first, next #3, finally #2 cylinder should follow in order by the same procedure.
(a) Remove the plug and rocker covers from the #1 cylinder.
(b) Turn the prop slowly forward by hand until the rocker arm of intake stops. Further turn the prop to bring the piston to
the TDC (Top Dead Center) of compression stroke.
(c) Use the attached wrench and hexagonal wrench to adjust the gaps indefi-
nitely close to zero within the range compression exists. If the gap is lower
than 0, the valve has to be opened at all phases so the compression
doesnt occur (then, loosen the screw to reset).
After adjustment, put on the spark plug and turn the prop forward to check
if the compression is enough.
(d) Checking the gap, securely tighten (but not excessively) the lock nut.
(e) Do the same adjustment for #3 cylinder.
(f) Finally do the same adjustment for #2 cylinder.
* In the case of the engines for vehicle, small gap is given to tappets to absorb valve elongation. However for SAITO engines,
gap becomes larger during operations due to thermal expansion of the cylinder (made of aluminum). Therefore set the gap
indefinitely close to zero when the engine is cold.
Tappet adjustment
Fig.10
Must not be inserted
(over gap)
Limit gauge
(0.1mm)
Close to "0" with no limit
Note: Occasionally check tappet gap by those procedure. When the attached gauge (limit gauge, t=0.1mm) comes to be inserted, gap has
been enlarged beyond the allowable limit. Make an adjustment to lessen the gap. Tappet gap is one of the most important factors in the
maintenance of 4-stroke engines. Operating the engine with the tappet gap enlarged excessively will cause poor performance or troubles.