YS 61ST-2 User manual

52mm
43.5mm 25mm
Hover Needle
Fuel Filter
Tube (B)
Tube (A)
Check Valve
Tube (C) 3 15/16"(10cm)
Low Needle
High Needle
Factory Set
Do Not Adjust
SPECIFICATIONS
Bore 24mm
Stroke 22mm
Displacement 9.95cc
Weight 540g
Practical rpm 2,000 ~18,000
OPERATOR’S MANUAL
61ST-2 (Helicopter Engine)
FEATURES
The 61ST-2 is the 2
nd
generation of the ST series. De-
signed from the ground up, the 61ST-2 will
meet all your helicopter competition needs. The 61ST-2
incorporated many features from the 61ST and more
● New short stroke piston and liner design
● New Carburetor with low end adjustment
● New Pressurized regulated and fuel injection system
● New 3 independent needle system
Besides that add more power and you have an
unbeatable performer.
INSTALLATION
1. The fuel lines should be connected to the fuel tank
as shown in the above figure. 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 tight to prevent pressures 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 3 15/16” or (10cc)
between the engine and check valve. DO NOT use
any other type of check valve. The check valve is
designed exclusively for the 61ST.
4. Adjust your throttle linkage and curve using the
alignment indentations on the carburetor body located
on the throttle arm side of the carb body.
PLEASE NOTE that the hover position is at 40% see
FIG 2.
START UP
1. Always remove Tube(A) at the check valve first before
fueling. The fuel tank is pressurized and you need to
relieve the pressure first. Disconnected Tube-b at the
filter and fill the tank. Reconnect Tube(A) and (B).
2. From the fully closed (clock-wise) position, turn the
needle valves counter clock-wise as follows.
STARTING SETTINGS / OPERATING SETTINGS
● Hover 1.75open 1.75 ~1.50
● Low 1.25open 0.75 ~0.50
● Full 1.5open 1.25 ~0.75
3. Close the throttle to the idle position and connect the
glow plug driver. The engine is now ready for starting.
BREAK-IN
It is not necessary to mount this engine on a set stand for
break-in. However, the engine should be adjusted slightly
on the rich setting for the first few flights to insure proper
break-in. Always use a good quality fuel which contain
15 ~30% nitromethan and an oil content of 20 ~23% low
viscosity oil.
NEEDLE VALVE ADJUSTMENT
Idle, Hover and High needle valves all work the same way.
Turning the needles clock-wise will lean the fuel mixtures
and counter clock-wise will richen the fuel mixtures.
1. Set needles as described in START-UP.
2. Start the engine and check idle. Adjust as needed.
3. Lift helicopter into a hover and check for the correct
rotor RPM recommended by the kit manufacture.
Once this is done take note of the amount of smoke
being produced by the muffler. The mixture is correct
for hover when there is a steady stream of smoke
being produced.
4. Land the helicopter for approximately 20~30 seconds.
Lift the helicopter into a hover again taking note of the
transition from idle to hover. If the engine exhibits a
large amount of smoke and the throttle response is
sluggish, you will need to adjust the idle and or the
hover needle leaner to achieved a smooth transition.
If the engine detonates and the smoke is inconsistent
or a small amount is produced, the mixture is to lean.
5. The high speed needle refines the fuel mixture for
forwardflightswithoutaffectingthehoveringadjustment.
After the engine is started and warned up, lift off into a
hover and check that the engine is running smooth with
a good trail of smoke. If everything is fine, open the
throttle and enter forward flight. Take note of the amount
of smoke like we did in a hover adjustment. It is correct
when you see a noticeable steady smoke trail.
Adjust the high-speed needle valve to obtain slightly
rich but consistent setting.
STOPPING THE ENGINE
1. Fully close the throttle barrel to stop the engine.
2. As soon as the engine stops running, be sure that a fuel
line clamp is used in Tube-B to prevent fuel from
flowing into the engine.
3. On the final flight of the day, the fuel line clamp should
be used to stop the engine in order to prevent rust and
corrosion.
FUEL AND GLOW PLUG
We have found that the fuel and glow plugs listed below
will give the best engine performance.
Fuel
Powermaster 30% Special Heli Blend
Cool Power 30% Special Heli Blend
Glow Plug
Enya #3
OS #8
OS-A3
IMPORTANT!
Silicone rubber is used in many parts of the YS engine.
Use only glow fuel of methanol for cleaning. Gasoline and
other volatile solutions will damage silicone if used.
Fig.1
Fig.2 High Speed 100%
Low Speed 0%
Hover 40%

3
9
6
7
8
9
10
5
1
28
27 29
25
2
26
30
33
32
31
29
4

36
19
20
21
34
22 23
24
11
17
16
18
4
2
43
13
35
40
37
39
38
41
12
14
15
WARRANTY
Strict quality control is implemented by our factory in all phases, from
parts manufacturing to final assembly. If performance deteriorates or a
part fails due to a manufacturing error, YS will repair or replace
the engine at no charge in the period of one year from date of purchase.
Warranty does not cover normal maintenance.
Should the engine be modified, incorrectly assembled or abused, there
will be a normal charge for parts and labor. The use of four cycle fuel
due to low oil content will also void warranty.
YS 61ST2-H Parts List
# PART# DESCRIPTION QTY
1 S8101 Crankcase 1
2 S7102 Cylinder Head 1
3 S7103 Head Gasket 1
4 R6104 Head Screws 6
S8105S Piston/Liner Set
5 S8105 Cylinder Liner 1
6 S8106 Piston 1
7 S7107 Ring 1
8 S7108 Wrist Pin 1
9 R6108 Wrist Pin Retainer 2
10 S8110 Rod 1
11 S8111 Crankshaft 1
12 R6112 Front Bearing 1
13 S7113 Rear Bearing 1
14 R6115 Drive Washer Spacer 1
15 R6217 Propeller Nut 1
16 S7116 Back Plate 1
17 R6119 Back Plate Gasket 1
18 R6120 Back Plate Screws 4
S8119S Carburetor Assembly
19 S8119 Carburetor Body 1
20 R6122 Carburetor Gasket 1
21 S8121 Throttle Barrel 1
22 R6124 Throttle Barrel Retainer 1
23 F1258 Throttle Stop Screw 1
24 F1259 Throttle Stop Spring 1
F1545S Needle Valve Assembly
25 F1545 Hover Needle Valve 1
26 F1546 Hover Needle O Ring 1
27 F1555 Hover Needle Seat 1
28 F1256 Hover Needle Seat O Ring 2
29 F1557 Needle Detent 2
30 S8130 High Speed Needle 1
31 R6203 High Speed Needle O Ring 1
32 S8132 Low Speed Needle 1
33 S8133 Low Speed Needle O Ring 1
34 F1260S Throttle Arm 1
35 S7132 Carburetor Screws 2
36 S7133 Carburetor Subplate 1
37 S7134 Regulator Subplate 1
38 S8138A Regulator Assembly
39 S7136 Diaphram 1
40 S7140 Regulator Gasket 1
41 S7139 Regulator Screws 4
42 S7143 Nipple/Washer 1
43 S7144 Check Valve 1
S7145 Gasket Set 3
S8146 O Ring Set 5
Specifications may be changed without pror notice. 99 F
YAMADA MFG.CO.,LTD
67 Tsuchitori Inuyama Aichi 484-0917 JAPAN
TEL: [phone] / FAX: [phone]