(2) Next, in the condition of (1), fully open the throttle valve, turn back the main needle to make the air-fuel mixture very rich in
the range where the engine does not stall (about 4,000 rpm). Operate in this condition with 2 (or more) tanks. (Conduct this
step checking the density of the exhaust and the breatherʼs waste oil (inky-black waste oil)).
(3) Next, after filling up the tank, re-start the engine. With the throttle valve fully opened, throttle the main needle and operate
the engine for one tank at 7500 ‒ 8,000 rpm.
(4) Next, after filling up the tank, re-start the engine. With the throttle valve fully opened, turn the main needle from the rich to
the peaks several times. When the peak become stable, open the throttle valve from low speed to high speed several times
to check the response. And gradually elongate the time of high-speed operation. Conduct this operation for one tank.
(5) When the revolution is stabilized at peak, the ground-level break-in is completed. After adjusting the tappet gap in the
manner of section “14”, adjust the carburetor according to the following section. The running-in is completed by performing
some 20 flights in a little rich condition. Subsequently, the flight should be performed in such a rich condition as far as not to
influence the flight.
13. Adjustment of carburetor
The principal method of adjustment is the same as that for our glow engine.
In principle, a carburetor is adjusted by first achieving peak (the highest revolution) with the main needle and then set idling
(low speed revolution) with the throttle valve and the slow needle. (Unless the peak is certainly achieved, idling adjustment will
be difficult and not stabilized.)
(1) After filling up the fuel tank, start the engine in the manner of Section “11” and then fully open the throttle valve with the
throttle stick.
(2) By turning the main needle depending on the tachometer and the exhaust sound, achieve peak carefully.
* As for adjusting the main needle in the case of actual flight, setting the peak in the perpendicular attitude with a propeller
in the upward direction is recommended if itʼs possible. In that adjusting, itʼll be rich enough in the horizontal attitude so
itʼs more similar to the condition during the actual flight.
(3) Next, close the throttle valve until the engine operates stably with an idling rotation of around 2000 - 2500rpm, adjusting
the slow needle with the (-) screw driver and the throttle valve carefully.
*Since the richness level of the air-fuel mixture varies corresponding to the nature of the airframe, please adjust it depending
on the userʼs skill.
Generally, in a scale flight in which the stability of a low-speed zone is considered as important and the engine is operated
slowly, adjust the air-fuel mixture to be relatively lean. In an acrobatic flight in which the early stand-up from a low speed is
considered as important, adjust the air-fuel mixture to be slightly rich.
(4) After the idling is set, get the throttle valve slowly fully opened. If the revolution becomes slow or goes up suddenly, adjust
carefully until it changes linearly from idling to peak, by fine-tuning with the slow needle.
(5) After the above adjustment is completed, open the throttle valve from idling to peak quickly. If the revolution does not
achieve peak immediately but get delayed as the throttle valve is fully opened, fine-tune the main needle and perform the
same process from idling to peak quickly. Repeat this carefully until the response improves.
* The key to make the engine last for long life is operating with the slightly rich condition as far as it doesnʼt effect to the flight.
Adjustment is needed depending on the engine attachment direction, the propeller, the fuel, the plug, the climate condition,
etc. During flights, please fine-tune so that low speed, medium speed, and high speed match best with the airframe.
14. 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.
(2) 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.
(3) Since the fuel contains more than 5% of oil, sometimes the exhaust valve gets dull by carbon or sludge especially in cold
atmosphere. Then turn off the ignition switch and rotate the prop by electric starter. After dilute the oil content by this way,
remove the fuel from inside the carb and the engine. It helps the valve to move smoothly.
Or, remove the rocker cover and applying some anti-rust spray to the exhaust valve is effective as well.
(4) 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 high quality oil.
(5) Charge the battery for the ignition system and RC device fully. (Since the ignition system generates high tension, be careful
of electrical shock.)
(6) 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 time of ascent should be a proper peak of the engine during flight.
(7) 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.
(8) Because all of SAITO gas-engines use oil-fuel mixture, there tend to be carbon buildup inside
the muffler as shown in the picture. It causes some problems on the exhaust outlet and
consequently reduces the power. Therefore cleaning/removing carbon every about 50 flights
is recommended. Using a parts cleaning spray is effective way. Actually, it depends on the
quality of the oil so when you feel the power loss, please check inside the muffler.
In the case of the picture which had been done more than 70 flights, by removing the carbon
buildup, the smoothness of the engine improved dramatically.
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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.
Caution: Over closing the main needle is very dangerous because it may cause knocking and propeller nut loosening. Then,
turn the main needle CCW immediately to make it rich a little.
