Yamaha F50 Service Manual
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62Y3A114-22 1 2 3 4 5 6 7 8 I 4. Push the throttle control lever 1 to the fully open position as shown. 5. While pushing the carburetor throttle lever 2 against the carburetor stopper 3 , loosen, and then tighten the adjusting screw 5 . Adjusting the pilot screw 1. Start the engine and warm it up for 5 min- utes to check the stability of the engine. Adjust the pilot screw if necessary. 2. Attach the special service tool to high- tension cord #1 1 . 3. Turn the pilot screws 2 in direction a until the engine idle speed has decreased to approximately 50 r/min, then in direction b 5/8 turn.4. Turn the throttle stop screw 3 in direc- tion c or d until the specified engine idle speed is obtained. NOTE: To increase the idle speed, turn the throttle stop screw in direction c . To decrease the idle speed, turn the throttle stop screw in direction d . 5. After adjusting the idle speed, rev the engine a few times and let it idle for at least 15 seconds to check the stability of the engine. Adjust the carburetor syn- chronization if necessary. Inductive self-powered tachometer: YU-08036-B Digital tachometer: 90890-06760 S62Y4350 1 Engine idle speed: 900 ± 50 r/min Carburetor
FUELFuel system 4-2362Y3A11 Synchronizing the carburetors 1. Start the engine and warm it up for 5 min- utes to check the stability of the engine. 2. Attach the special service tool to the high-tension cord #1 1 . 3. Remove all of the plugs 2 and attach the special service tool and adapters to the carburetor assembly as shown. NOTE: For best results, use a vacuum gauge 3 (commercially obtainable) with four adapters like the one shown in the illustration. 4. Adjust the idle speed to 1,000 r/min by turning the throttle stop screw 4 on car- buretor #4 in direction a or b . NOTE: To increase idle speed, turn the throttle stop screw in direction a . To decrease idle speed, turn the throttle stop screw in direction b . Inductive self-powered tachometer: YU-08036-B Digital tachometer: 90890-06760 Carburetor synchronizer: YU-08030 Vacuum gauge: 90890-03159 S62Y4380 1
62Y3A114-24 1 2 3 4 5 6 7 8 I 5. Measure the vacuum pressure of carbu- retor #4. 6. Turn the throttle valve adjusting screws 5 to adjust the vacuum pressure of car- buretors #1, #2, and #3 to the same vac- uum variation as carburetor #4. 7. Adjust the engine idle speed to specifica- tion. 8. After adjusting the idle speed, rev the engine a few times and let it idle for at least 15 seconds to check that the vac- uum pressures stay within 50 mm Hg (67 m bar, 1.97 in Hg) and to check the stability of the engine. Adjusting the dash-pot (acceleration pump) 1. Start the engine and warm it up for 5 min- utes, and then check the engine speed at the operation point of the dash-pot. 2. Attach the special service tool to high- tension cord #1 1 .3. Open the throttle cam 2 slowly, and check the engine speed when the accel- eration pump stopper 3 comes into con- tact with point a . 4. If out of specification, adjust the engine speed at the operation point of dash-pot. Engine idle speed: 750 ± 50 (950 ± 50) r/min Inductive self-powered tachometer: YU-08036-B Digital tachometer: 90890-06760 Engine speed: 2,700 r/min S62Y4430 1 Carburetor
FUELFuel system 4-2562Y3A11 5. Open the throttle cam 2 slowly, and check that the acceleration pump stopper 3 comes in contact with point a . 6. Turn the adjusting screw 4 in or out until the specified engine speed is obtained. 7. Open and close the throttle cam a few times, and check the engine speed at the operation point of dash-pot again. Adjust if necessary.
POWR 62Y3A11 Power unit Troubleshooting ............................................................................................. 5-1 Special service tools ................................................................................... 5-10 Power unit ..................................................................................................... 5-13 Checking the compression pressure ....................................................... 5-25 Checking the oil pressure ........................................................................ 5-25 Removing the power unit ......................................................................... 5-26 Timing belt and sprockets........................................................................... 5-29 Removing the timing belt and sprockets.................................................. 5-31 Checking the timing belt and sprockets ................................................... 5-32 Installing the timing belt and sprockets.................................................... 5-32 Cylinder head ............................................................................................... 5-35 Removing the cylinder head .................................................................... 5-39 Checking the valve springs...................................................................... 5-40 Checking the valves ................................................................................ 5-40 Checking the valve guides....................................................................... 5-41 Replacing the valve guides...................................................................... 5-41 Checking the valve seat .......................................................................... 5-42 Refacing the valve seat ........................................................................... 5-43 Checking the rocker arms and rocker arm shaft...................................... 5-45 Checking the camshaft ............................................................................ 5-45 Checking the cylinder head ..................................................................... 5-46 Checking the oil pump ............................................................................. 5-47 Installing the valves ................................................................................. 5-47 Installing the camshaft ............................................................................. 5-48 Installing the rocker arm assembly .......................................................... 5-49 Installing the cylinder head ...................................................................... 5-49
62Y3A11 1 2 3 4 5 6 7 8 I Cylinder body ............................................................................................... 5-51 Removing and installing the oil filter ........................................................ 5-55 Disassembling the cylinder body ............................................................. 5-55 Checking the piston diameter .................................................................. 5-56 Checking the cylinder bore ...................................................................... 5-56 Checking the piston clearance ................................................................ 5-57 Checking the piston rings ........................................................................ 5-57 Checking the piston ring grooves ............................................................ 5-58 Checking the piston ring side clearance .................................................. 5-58 Checking the piston pin boss bore .......................................................... 5-58 Checking the piston pin ........................................................................... 5-58 Checking the connecting rod small end inside diameter ......................... 5-59 Checking the connecting rod big end side clearance .............................. 5-59 Checking the connecting rod bolt ............................................................ 5-59 Checking the crankshaft .......................................................................... 5-59 Checking the crankshaft main journal oil clearance ................................ 5-60 Checking the crankshaft pin oil clearance ............................................... 5-61 Selecting the crankshaft main journal bearing......................................... 5-62 Selecting the connecting rod big end bearing ......................................... 5-63 Assembling the cylinder body .................................................................. 5-64 Installing the power unit ........................................................................... 5-67
POWRPower unit 5-162Y3A11 Troubleshooting5 Before troubleshooting the power unit, check that all electrical connections are tight and free from corrosion, and that the battery is fully charged to 12 V. Symptom: Engine does not crank. Check the starting system. Check the power unit. Check that the gearshift is in the neutral position. Check the neutral switch for continuity. Check the engine start switch for continuity. Check the engine shut-off switch for continuity. Replace the engine shut-off switch. Is the gearshift in neutral? Is there conti- nuity? Is there conti- nuity? Is there conti- nuity? Is there conti- nuity? Set it to the neutral position. Replace the neutral switch. Replace the engine start switch. Replace the fuse. Yes Yes Yes No Yes No No No Yes No Continued on next page. Check the fuse for continuity.
62Y3A115-2 1 2 3 4 5 6 7 8 I Check the wiring harnesses for continuity. Replace the wiring harnesses. Check that the combustion camber is filled with engine oil or gasoline. Check the starter motor. Check operation of the starter motor pinion. Remove all spark plugs, and then the engine. Listen for the operation sound of the starter relay. Check the power unit. Is there conti- nuity? Can the oper- ation sound be heard? Does the pin- ion rotate? Replace the starter relay. Does the engine crank? Yes Yes Yes Yes No No No No Troubleshooting
POWRPower unit 5-362Y3A11 Symptom: Engine cracks, but will not start. Check the ignition system. Check the fuel system. Check the compression pressure of power unit. Wet spark plugs? Does the engine start? Wet spark plugs? Out of specifi- cation? Out of specifi- cation? Check the condition of the spark plugs. Check the fuel system. Failure in starting operation Failure in starting operation Check the fuel system. Check the condition of the spark plugs again. Check the compression pres- sure of the combustion chamber. Check the ignition system out- put peak voltage. Check the valve clearance. WARNING •Do not touch any of the connections of the spark gap tester leads. •Do not let sparks leak out of the removed spark plug caps. •Keep flammable gas or liquids away, since this test can produce sparks. Start the engine using dried or new spark plugs. Adjust the valve clearance. No No No Yes Yes Yes Yes No Yes No No Check the ignition spark using the spark gap tester. Below the spark gap specification? Yes Check the cylinder head, cylinger body, and piston assembly.