OPERATOR'S MANUAL
50ST
(Part No.YS0030)
42.3
17.5
37
Fuel Filter
Low Speed Needle
Main Needle Valve
Tube (B)
Tube (A)
Check Valve
Tube (C) : 35mm
37
44
FEATURES
The YS 50ST Engine features the patented YS regulated
fuel system for positive fuel flow during all types of flight
conditions.
Factory authorized parts and service available worldwide.
CAUTIONS
1. Take care not to touch the engine immediately after shut-
down to avoid painful burns.
2. Do not attempt to fly with engine problems as it can be
dangerous. Fix the problem prior to flying.
3. When starting the engine, do not use full throttle but set
throttle to low speed before applying the glow driver.
4. This engine is intended for helicopter use. Aircraft conver-
sion parts are available from our service department.
5. This engine is intended for use by experienced modelers
only. If you are not properly trained to operate this engine,
please get assistance from a skilled modeler.
6. The user is responsible for operating this engine in a safe
safe manner.
INSTALLATION
1. The fuel lines should be connected to the fuel tank as
shown in the above diagram. Be careful to install the
check valve in the correct direction. Since the tank is
exposed to high pressures, be sure that all connections
are secure to prevent pressure leakage.
2. Since the engine is sensitive to dirt in the fuel, a fuel filter
must be used.
3. Tube (C) should be set exactly at 35mm between the
engine and the check valve.
4. The check valve is designed exclusively for the 50ST.
Use only YS factory parts for replacement.
MUFFLER
1. Use an expansion chamber muffler intended for 50 size
helicopter engines. If there is a fuel tank pressure fitting
on the muffler you choose, plug it, as it is not necessary
to use muffler pressure with the YS system.
2. Please note that the use of tuned pipes and tuned muffler
systems can interfere with the operation of the regulator
system and result in poor engine performance.
STARTING PROCEDURE
For the best overall performance with your 50ST Helicopter
Engine, we recommend 30% nitro fuel blended especially for
helicopter use. Lower nitro percentages may be used, but
reduced performance will result.
1. Always remove tube (A) at the check valve first. The fuel
tank is pressurized by the engine and you need to relieve
the pressure. Then, disconnect tube (B) and fill between
the filter and the tank. If you make a mistake in the proce-
dure, fuel will squirt out. An easy method is to use T-Fittings
tings between the check valve and the tank, and between
the fuel filter and the tank with plugs that can be removed
for pressure relief and fuel filling.
2. From the fully closed (clockwise) position, open the main
needle valve 1,75 turns. Close the idle needle fully (clockwise)
and open 1 turn.
These are the initial settings and will be re-adjusted as you
set up the engine and helicopter.
3. Open the throttle fully and run the engine with an electric
starter for about 10 seconds without connecting the glow
driver. This pressurizes the fuel tank and the engine is now
now ready for starting. Set the throttle barrel to low speed
and connect the glow driver before starting the engine
with the electric starter.
4. If the engine refuses to start, remove the glow driver, open
the main needle valve 2 turns from its present setting and
repeat Step 3. Return to low throttle and start the engine.
After starting, return the main needle to its running setting
before advancing the throttle.
IDLE ADJUSTMENT
Begin with the idle needle with 1 turn open from closed
(clockwise) and adjust from that point. Turning this needle
clockwise will lean the fuel mixture, and counter-clockwise
will richen the fuel mixture. Changes in fuel and weather
conditions may require re-adjustment.
HOVER ADJUSTMENT
Hover is adjusted with the main needle valve. There is some
interaction between the hover setting and full throttle setting,
so be aware that one adjustment will affect the other.
HIGH SPEED ADJUSTMENT
High speed is also adjusted with the main needle valve.
Turning the needle valve clockwise will lean the fuel mixture,
and counter-clockwise will richen the fuel mixture.
Adjust carefully as this setting will also affect the hover ad
-
justment.
THROTTLE LINKAGE
Set the throttle stick on the transmitter at the center, and
adjust the linkage to put the mark on the carb body and the
mark on the throttle barrel in line. Hovering should take place
with the throttle stick near the center position if the linkage
ratio is properly set. If the ratio is incorrect, the throttle bar-
rel will be too far open at the center position on the stick and
hovering will commence at a lower stick position.
Fig.2
BREAK-IN
It is not necessary to mount this engine on a test stand for
break-in. However, the engine should be adjusted slightly on
the rich setting for the first few flights to ensure proper break-
in. Always use a good quality fuel which contains 30% nitro
and an oil content of 20-30%.
GLOW PLIG
1. We have found that the glow plugs listed below will give
the best engine performance;
YS #2
OS #8
Enya #3
2. Replace the glow plug when idling or top end performance
decreases.
IMPORTANT!
Silicone rubber is used in many parts of the YS Engine. Use
only glow fuel for cleaning. Gasoline or other solvents will
damage silicone if used.
Fig,1
SPECIFICATION
Bore 22,0mm
Stroke 21,5mm
Displacement 8,17cc
Weight 398g
Practical rpm 2,000-20,000rpm
B
A
High Speed 100%
Hover 40%
Low Speed 0%
