YS Engines FZ91 Drive Washer Retainer User Manual

Engines FZ91 Drive Washer Retainer
User Manual

**SPECIFICATIONS

**

FEATURES

The FZ91 is the most powerful 91 four cycle engine available.
This engine offers many exclusive features that have been proven on other YS engines.
Supercharged system with simplified structure to keep weight to a minimum while still retaining maximum efficiency.
Air chamber that uses crankcase pressure coupled with a double throttle valve system which allows a bigger charge of fuel and air mixture to enter the intake valve for more power.
Same proven piston design as the 140Limited which creates more crankcase pressure for a more consistent fuel flow to the regulator.
Fuel injection system for superior throttle response. This system is unaffected by tank position or by the attitude of the model.
GROW PLUG
Select the most appropriate glow plug from those designed specifically for 4 cycle engines. GLOW plug selection greatly affects the maximum engine output and low idle. If RPM’s decrease or stop when the booster cord is removed, replace the plug. We recommend YS #4 (P0040).

INSTALLATION

1. Connect the engine to the tank as shown in fig.1. Since high pressure is applied to the tank, tighten all connections carefully. Care must be taken to prevent pressure leakage due to undertightening of the check valve or by kinking the fuel lines.
2. Always uses a fuel filter. We recommend the YS filter.
3. Match the direction of the check valve arrow to fig.1, with the arrow facing towards the tank.

PROPELLER INSTALLATION

Due to the high torque of the FZ91 engine, we have equipped it with double locknuts for safety.

1. Mount the propeller and tighten the rear nut. Next, tighten the front nut as shown in fig.2.
2. Select a good quality propeller that will turn in the 8,000 to 11,000rpm range. We recommend sizes 13~12-14, 13.5~10-14, 14~10-14.

START-UP

1. Remove tube(B)from the filter;remove tube(A)from the check valve, then fill the tank.
   Caution:If tank is filled or under pressure remove tube(A) first; then tube(B). Fuel will eject if tube(B)is removed first while the tank is pressurized.

2. Open the needle valve 1 1/2 from the fully closed position.

3. Open the throttle fully and slowly turn the propeller ten turn. This primes the system by pressurizing the tank and sending fuel to the carburetor.

4. Pour several drops of fuel into the carburetor.

5. Close the throttle to the idle position and connect the glow plug cord. The engine is now ready for starting.

Do not attempt to start at full throttle, as this is very dangerous.
BREAK-IN
To maximize engine performance and increase durability, please follow this break-in procedure:

1. Use the same size(or slightly smaller) propeller than you intend to use in flying.
2. Use a good quality fuel which contains 15-20% nitromethane and an oil content of 15-20%. Synthetic or castor oil can be used, or a combination of synthetic and caster. Do not use four cycle fuel due to low oil content.
3. The needle valve should be set so that the engine is running at a rich setting. Run the engine approximately 20 minutes with this setting.
4. Mount the engine to the model and fly ten times with this setting. This concludes the break-in procedure. It is advisable to always use a slightly rich setting to keep the moving parts lubricated, even after the break-in period.

HIGH SPEED ADJUSTMENT

1. Adjustment of high speed is done by the carburetor needle valve. When the needle valve is turned clockwise, the mixture is leaner. When it is turned counterclockwise, the mixture is richer. A good starting position for the high speed needle valve is 1 1/2 turns open from fully close position.
2. When the engine is started, open the throttle gradually. Next, find the peak position(highest RPM) by adjusting the needle valve. Then the needle valve should be opened approximately 1/8 of a turn from full RPM to achieve best performance. The engine may stop if the throttle is opened to full immediately after starting. Wait unit the engine temperature rises and then open the throttle slowly.
3. For flying, it is advisable to use a slightly richer mixture setting. By using a richer mixture, the engine temperature is maintained and RPM stability improves.

LOW SPEED ADJUSTMENT
This engine is equipped with a new low speed needle valve to adjust the mixture from low to mid throttle. This needle valve is located on the side of the throttle barrel opposite the throttle arm(fig.1).

1. Open the low speed needle to 1 1/2 turns from fully closed position.
2. The low speed needle valve should be set after the high speed needle valve has been adjusted. Close the throttle gradually to a idle(approximately 2500rpm). Let it idle for 20 to 30 seconds and then slowly advance the throttle. The adjustment is satisfactory at low speed if transition is smooth at this time.
3. If the engine is running rough on idle, the low speed mixture is rich. If the engine starts to speed up and dies on idle or starts to detonate, when advancing the throttle, the  mixture is lean. Turn the low speed needle valve clockwise to richen and counterclockwise for a leaner mixture(note that the direction of the low speed needle valve is opposite the high speed needle valve). Adjustments to the low speed needle valve should be 1/8 to 1/4 of a turn increment at a time to achieve smooth throttle response.

IMPORTANT! The regulator adjusting screw on this engine is factory set. No further adjustments are necessary. If for some reason you have to disassemble the regulator assembly, the regulator adjusting screw should be set flush with the regulator body.

TAPPETCLEARANCE ADJUSTMENT

1. Tappet clearance is factory preset. No adjustment is necessary unit after 1 hour of operation(includiing break-in period).
2. Clearance adjustment should be done when the engine is cool. When the engine temperature is high, clearance is higher due to thermal expansion.
3. The proper clearance setting should be at 0.04-0.1mm. The adjustment is achieved by loosing the locknut(fig.3) and turning the adjusting screw.Tighten the locknut after the adjustment is achieved. After the initial 1 hour adjustment, this procedure should be performed after every 2 hours of use.

DIAPHRAGM AND CHECK VALVE DISASSEMBLY

Diaphragm:

1. Remove the adjustment screw of the valve, and then remove the inside valve and spring.
2. Clean the inside with alcohol or appropriate cleaner. Reassemble.
3. Screw in the regulator screw until flush with the diaghragm body.

Check valve:

1. Open the valve by rotating the body counterclockwise.
2. Reassemble the check valve carefully.

IMPORTANT! Silicone rubber is used in many parts of the YS engine. Use only glow fuel or methanol for cleaning. Gasoline and other volatile solutions will damage the silicone if used.

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.
Should the engine be modified, incorrectly assembled or abused, there will be a nominal charge for parts and labor. The use of four cycle fuel due to the low oil content will also void warranty.

TEL (0568)67-0265
FAX (0568)67-7801
YAMADA MFG. CO.,LTD.

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