The YS .91 SR is the latest big block engine from YS. This engine is a very user friendly with respect to tuning.  Please follow the factory recommended settings for break in procedure.

Listed below are the settings I have found to work well using the following equipment. Enya 3 plug, Hatori SB-19, cool power 30% fuel also a futaba gv-1 governor. After break in, this should only take a few gallon’s, you can start leaning the engine down a little.

• Low end – 1.25/1.00 from fully closed
• Midrange – 1.75/1.5 from fully closed
• High end – 1.0/0.75 from fully closed

Remember these settings are approximate settings as temperatures change so will your engine settings. Remember that hot you need to lean, cold you need to richen.

Gear ratio testing I have found through extensive testing, that 8.0 to 8.2 will deliver the ultimate performance for 3D flight. I run no more than 1850 on head speed and this seems to work very well.

The YS 50 ST is the second generation of the 50 Series. I have been flying this engine in my Raptor 50 and the power delivery and fuel economy are excellent. I recommend running a Hatori SB-15 on this engine.

Break-in Procedure: After running a tank of fuel, bring the helicopter into a hover and look for a solid smoke trail. You should also pay close attention to the sound of the engine. A lean condition will make the engine sound raspy, and a rich condition will gurgle and be unresponsive. At this point you will want to tune the high-end needle until you get a nice smooth run in a hover and top end power.
Most common fuel system problems: Cracked fuel tank: Split at a seam Clunk line hitting back of tank: As fuel line gets older if will stretch and go soft. Fuel line and Fuel line “T”s: Not holding pressure. Silicone Rubber: I have found many engines plugged up with bits of silicone. Diaphragm: Check for cracks or torn around the edges. Regulator Gasket: Plugging up holes for fuel and or pressure. Dirt in Carb: Yes even if you have fuel filters. Using in-line fuel filters is a good way to prevent junk from getting into the carb but remember, anything that can go into the carburetor can make it’s way to the fuel regulator. I have seen the following stuck in regulators and inside engines: Grass, Paint chips, Mud, Silicone Rubber ect…** I recommend using Cool Power 30%, a Hatori muffler and an Enya #3 glow plug. I have found that this combination provides reliability, excellent power, and exhaust note for the 90SR and the 50ST.

Set limit on gyro to max (140%) set delay pot for 3d use to 0. Use pickoff point on servo arm for full deflection of both right and left rudder. Make sure the gyro direction is correct. Set gain to 50% for the starting point. Set rudder end point to 100% for a good start setting.

Step 1: Set gyro direction

Step 2: Set mode to (AVC)

Step 3: Set flight mode to 3D

Step 4: Set limit A, B anything over 120% is good

Step 5: Set gain to 35%, no more than 37% gain is needed.

Set start delay both A and B to 15%

Set stop delay both A and B to 40%

Note:
Start and stop delays are needed when flying a helicopter with a very stout torque tube design. Keep in mind that increasing the rudder end point will give you a faster pirouette rate on both gyros.

Set head speeds, example Norm 1550
Idle1 1750
Idle2 1850
GRT – Set gear ratio
SWPT – Switch point, turn on
STSW – Stick switch, activate if using the stick as a switch
SwCd – Use to check status & verify GV-1 is working properly
Limit Idle/High/Cut – Set idle, full throttle, and cut positions.
Check that the sensor is reading is at 97%

Note:
To reset the GV-1 & GY-601, Transmitter is on, helicopter is off. Hold down both function keys & power up the helicopter till the GV-1/GY-601 screen flickers, about 3 seconds. Click function key until RESET appears. Then click the data key once, it will ask are you sure you want to reset? Click the data key again to reset all settings to factory defaults.

Tip: Your helicopter will only perform well if you spent the time making sure its built correctly and set up right. Take the time to learn the building and set-up process. Don’t just focus on flying.