SERVICE BULLETIN REFERENCES 17-1

Transcription

1 SERVICE BULLETIN REFERENCES 17-1

2 ENGINE TEAR DOWN Engine tear down and assembly is easy if done right. Use the right tools, disassemble in correct order, and remove complete assemblies intact where possible. Proceed as follows: C SERIES ATURN FUEL VALVE OFF AND DISCON- NECT GAS LINE FROM CARBURETOR, REMOVE CHOKE ROD FROM CHOKE SHAFT, AND REMOVE COMPLETE ENGINE SHROUD, GAS TANK AND RECOIL STARTER AS AN ASSEMBLY. SPARK PLUG AND INSTALL PISTON STOP PART NO REMOVE FLYWHEEL NUT AND WASHER. LIFT STARTER PULLEY, PLATE, SCREEN PIN AND SPRING OFF FLY- WHEEL. REMOVE FLYWHEEL. PLACE NUT ON CRANKSHAFT NEARLY FLUSH WITH TOP CRANKSHAFT. LIFT UP ON FLYWHEEL, TAP SHARPLY ON THE NUT WITH A SOFT HAMMER. THE FLYWHEEL SHOULD SNAP LOOSEASILY. REMOVE FLYWHEEL KEY WITH PAIR OF SIDE CUTTERS OR DIKES. LIFT GOVERNOR YOKE, FLYWEIGHTS AND COLLAR OFF AS AN ASSEMBLY. SET ASIDE CAREFULLY. GOVERNOR SPRING SERVICE BULLETIN REFERENCES

3 ENGINE TEAR DOWN C SERIES REMOVE GOVERNOR LEVER AND WEAR BLOCK ASSEMBLY. EXAMINE WEAR BLOCK. IF WORN ON ONE SIDE TURN OVER. IF BOTH SIDES ARE WORN RE- PLACE. COMPLETE MAGNETO PLATE BY RELEASING THREE SCREWS. NOTE APPLY THREE OR FOUR DROPS OF 20 OR 30 WT OIL TO OILER AND REED PLATE ASSEMBLY. CONNECTING SCREWS. USE CORRECT SIZE DRIVER. ROD CAP SCREW NOTE CONNECTING ROD BEARING IN- CLUDES 33 LOOSE NEEDLES. EX- AMINE FOR WEAR..RE-INSTALL BYUSINGHEAVYGREASE. PLACE 17 NEEDLES ONROD CAP AND 16 ON ROD. VERY EARLY MODEL ENGINES WILL NOT HAVE NEEDLE BEARINGS. REMOVE CYLINDER HEAD BOLTS AND GASKET. SERVICE BULLETIN REFERENCES 17-3

4 TEAR DOWN C SERIES REMOVE PISTON, ROD AND RING AS- SEMBLY FROM CYLINDER. NOTE: Pull the piston and connecting rod assembly out quickly or the rings may bind or break. REMOVE THE CRANKSHAFT FROM THE CRANKCASE THROUGH THE TOP. EARLY MODELS LATER MODELS THE ENGINE ISNOW COMPLETELY DISASSEMBLED INTO ITS MAJOR PARTS SERVICE BULLETIN REFERENCES

5 REASSEMBLY.TIPS C MODEL ENGINES CHECK INTAKE PORTS ON NEW CYLINDER FOR BURRS AVOID SCORES. I CORRECTLY ALIGN CYL- INDER AND REED PLATE GASKETS MUST NOT BLOCK OIL PASSAGES. \ CHECK OIL PASSAGES OIL CONNECTING ROD MUST BE CLEAR FREE AND THE CRANKSHAFT OF DIRT. INSERT CRANKSHAFT CAREFULLY THROUGH OIL SEALS TOP AND BOTTOM AVOID SEAL DAMAGE. POSITION KEYWAY AND KEY EXACTLY BEFORE INSTALLING FLYWHEEL. USE ALL NEW GASKETS. TIGHTEN SCREWS, NUTS AND BOLTS refer to torque chart, SECTION 16. CHECK GOVERNOR FOR CORRECT ENGINE R.P.M. ADJUSTMENT TAKES TIME IF RE- QUIRED AFTER ASSEMBLY COMPLETED. RECOMMENDED ENGINE SPEED IS R.P.M. IF ENGINE RUNS ABOVE 3300 R.P.M. THE BLADE TIP SPEED WILL EXCEED THE FEDERAL SAFETY STANDARDS OF 19O00 FT. PER MINUTE. ON DRY TYPE AIR FILTER EQUIPPED ENGINES, REPLACE FILTER ELEMENT ON ENGINE OVERHAUL. SERVICE BULLETIN REFERENCES 17-5

6 f \ REPAIRING ENGINES WITH NEEDLE BEARING CON- NECTING ROD ASSEMBLY t BEARING R NEEDLE BEARING STRIP i Always check needle bearings and retainers on engine overhaul. Before removing connecting rod from crankpin, see if needles can be cocked or separated more than diameter of one needle. After removal, look for discoloration from heat, scoring or flat spots on needles. Replace needle bearings and bearing retainers as complete sets only. Needle bearings, precoated with grease, are supplied in strips of 33 (one set). INSTALLATION OF NEEDLE BEARINGS Press bearing retainers into connecting rod and cap. Be sure dove-tail ends of retainer halves match when mating marks on connecting rod and cap match. NOTE: Check crankcase for needle bearings that may have dropped inside during disassembly-. Lay bearing strip on forefinger. Carefully peel off backing. Curl finger around crankpin so needles transfer and stick to pin. ing rod to cap. Check crankcase for needles that may have dropped out during assembly. Oil after assembly. loosening of the screws SERVICE BULLETIN REFERENCES

7 GOVERNOR OPERATION A governor is simply a device which will automatically increase the power output of an engine when an additional load is put on the engine, and decrease the power output when the load is lightened. Different governors are used on the "C" and "D" Series Lawn-Boy engines, though all operate on the same principle. For flywheel removal see page Basically, the governor operates through weights which pivot out from the rotating crankshaft. When the engine is under -no load, the crankshaft rotates faster and the centrifugal force swings the weights out. Under load, the crankshaft rotates slower, and the weights drop in. The weights move a collar up- or down on the crankshaft. This collar is linked to the carburetor throttle disc. As the weights drop in, the linkage opens the throttle disc more, causing the engine to pick up speed until it reaches the correct operating RPM's. The action of the governor is continuous. There should be very little noticeable variation in RPM's of the engines, since any slight increase or decrease in RPM's is immediately transmitted to the carburetor. C SERIES GOVERNOR Engine speed should be 3200 RPM or 2800 RPM. This difference is accomplished with the spring. In other respects the governors are identical. The 2800 RPM spring is color coded (RED); the 3200 RPM spring is un- FREE LENGTH FREE LENGTH colored. If spring is distorted, replace. DO NOT ATTEMPTO ADJUST 3/4 IN..015 IN..765 IN..015 IN. GOVERNOR BY STRETCHING SPRING. GOVERNOR ADJUSTMENT Special' tool part # must be used for GOVERNOR checking the governor adjustment on "C" Se- ADJUSTMENT ries engines. With the governor assembly in place slip the gauge onto the crankshaft and hold down firmly. Holding the gauge in place, depress the throttle shaft to the closed throttle position, and raise the governor lever upward /16 INCH GOVERNOR ROD with,light pressure. If the governor is properly adjusted, there should be approximately 1/8 3/16 inch between the top of the governor rod and the bottom of the governor lever. To make any necessary adjustments simply bend (the governor lever is creased diagonally to simplify adjustment bend lever along crease) the governor lever up or down with a pair of pliers to obtain the proper clearance. SERVICE BULLETIN REFERENCES 17-7

8 GOVERNOR SERVICING Normally, little trouble is experienced with governors. Often engine surging is blamed on the governor when carburetion is at fault, If the governor is suspected, check the following: BINDING OF YOKE, WEIGHTS, OR COL- LAR, Check for burrs or distortion, or binding of arm at screws. BINDING OF ROD AT CARBURETOR MOUNTING SCREW, MAGNETO PLATE, OR THROTTLE SHAFT LEAF. Check for burrs. There should be no washer under the reed plate mounting screw nearest governor rod. EXCESSIVE WEAR ON WEAR BLOCK. This can be caused by surging, or rough collar surface. A rough collar can be honed smooth. Apply a light film of grease after honing. If the block is worn just from long usage, it can usually be inverted on the lever. CARBURETOR THROTTLE DISC BIND- ING IN CARBURETORTHROAT. This is not a governor malfunction, but may give the same symptoms, such as surging. See Carburetor Section. GOVERNOR REASSEMBLY Reassembly governor of the is easier if the In assembly be sure to push the coil wire spring is placed on the crankshaft, and the down below and away from the arc of the yoke, weights and collar assembled sepaweights..otherwise the movement of the rately. Grasp the assembly by the wide weights could wear through the insulation on sections of the weights and slip over crankthe wire. shaft and spring SERVICE BULLETIN REFERENCES

9 STARTER PRINCIPLE OF STARTER OPERATION The recoil starter does away with winding a rope around a pulley to start the engine. It consists of a handle attached to a rope, wound around a pulley, and a rewind spring to recoil the rope. A spring loaded pin attached to flywheel engages with starter pulley to turn flywheel and start engine. As soon as the engine starts, centrifugal force moves the pin outward, disengaging it from the starter pulley. C-12 AND LATER TYPE ROPE ANCHOR AT PULLEY EXPLODED VIEW The C-12 and later type starter has a larger, two piece pulley. The rope is "locked" in the handle and at the pulley by PRESSING into place. No clamps are required. ROPE ANCHOR HANDLE AT SERVICE BULLETIN REFERENCES 17-9

10 STARTER AND SHROUD There were two methods of attaching the rope to the pulley; a bead stop and a rope clamp. The rope clamp was an improvement over the bead clamp. C-10 STARTER BEAD STOP FIRST METHOD ROPE CLAMP SECOND METHOD Do not attempt to use the new clamp on an old pulley (with bead), unless the center section is first ground down 3/64 to relieve binding. STARTER ROPE '9 A new spring was also used, with a different method of anchoring on the starter housing. This spring allowed more flexibility under reverse force if the starter handle was allowed to "snap back." OLD SERVICE BULLETIN REFERENCES

11 DISASSEMBLY AND ASSEMBLY HINTS Both types are disassembled and assembled in about the same way, except for anchoring the rope. On later models it is necessary to remove the shroud before removing the starter. Remove the three screws as shown and lift starter from base. To remove pulley, take out pulley cap screw. SAFETY WARNING: WHEN REMOVING PULLEY AND SPRING, BE VERY CAREFUL OF SPRING. THE SPRING IS COILED UNDER TENSION IN THE CAP. LEAVE SPRING IN CAP UNLESS IT IS TO BE RE- PLACED. The rope should be singed a full 3/4 inch at both ends, to be sure it will hold securely. SERVICE BULLETIN REFERENCES SAFETY RELATED 17-11

12 DISASSEMBLY AND ASSEMBLY HINTS To replace spring in starter cap, proceed as follows: 1. With rope anchored and wound in pulley, place inside loop of spring in hub of pulley as illustrated for each type starter. 2. Place pulley on starter cap so that spring runs through slot in cap. 3. Secure pulley to starter cap with pulley bearing, washer and screw. Tighten screw securely. c-12 c With a firm grip on the cap, pull rope to 5. Rewind rope on pulley and continue until turn pulley. The turning pulley will draw the spring has been fully drawn in. the spring into the cap. 6. With rope fully wound on pulley, turn pulley against spring tension and with rope handle in slot, place starter on base. Hold starter on base and "feel" for proper tension. There must be some tension on spring, otherwise handle will not return all the way to starter when released. NEVER WIND PULLEY OVER TWO TURNS AFTER TEN- SION IS FELT ON SPRING. 7. Replace screws in cap to' base. RIGHT (OUTSIDE RATCHET) ON ALL STARTERS, MAKE SURE PIN OR PINS ON FLY- WHEEL PULLEYS ARE ON OUT- SIDE OF STARTER PULLEY RATCHETS, BEFORE TIGHT ENING STARTER TO SHROUD SCREWS. WRONG (INSIDE RATCHET') SERVICE BULLETIN REFERENCES