This manual covers the following basic type or model numbers dependent on age of product: AH520, AH600, AV520, AV600, HSK600, TVS600. This manual covered many engines under an Old form of Identification which will need to be reviewed as well. TYPE / SPECIFICATION NUMBER 638-670 1398-1642 and Craftsman 200 Series Models. General Information, engine identification, interpretation model of number, engine care, short blocks, storage, tune up procedure, exhaust port cleaning, cycle theory of operation, operation of piston port style, operation of reed ported style with loop scavenging, terms, exhaust or scavenge phase, ports, exhaust ports, third port, reed valve, lubrication, air cleaners, carburetors, governors and linkage, air cleaners. General carburettor information, Float type carburetors, Diaphragm, carburetors, inlet needle and seat (float carburetors, needle and seat opo-off test, float height settings. Linkage installation, rewind starters, components, rope service, stylized rewind starter. Electric starters. Drive assembly service, starter checking and service, check field armature check, troubleshooting starters, alternators, checking the system, flywheel (inside-edge) brake system, Inside edge system, components service control cable. Ignition, ignition service, troubleshooting engine fails to start or starts with difficulty, engine knocks, engine misses under load, engine lack power, engine overheats, specification, and more. complete service manual consist of 68 pages in pdf format. Contents PRIMER BULB (DIAPHRAGM CARBURETOR) 11 CARBURETOR CHECK VALVE11 CARBURETOR SERVICE PROCEDURE 12 EMISSIONIZED DIAPHRAGM CARBURETION13 OUTBOARD CARBURETORS 13 OUTBOARD CONTROL PANEL 14 CARBURETOR ADJUSTMENTS 15 IDLE SPEED ADJUSTMENT 15 FLOAT TYPE-FIXED MAIN, IDLE ADJUST 15 DIAPHRAGM - SINGLE AND DUAL ADJUSTMENT 15 TROUBLESHOOTING CARBURETION 16 FLOAT CARBURETOR CHECKS 16 CHECKS FOR DIAPHRAGM 16 STANDARD SERVICE CARBURETORS17 FUEL FITTING 17 INLET FUEL FITTING17 CHOKE SHAFT17 THROTTLE LEVER 17 IDLE SPEED ADJUSTMENT SCREW 17 GOVERNORS AND LINKAGE 18 AIR VANE GOVERNORS 18 OPERATION18 LINKAGE INSTALLATION 18 REWIND STARTERS, ELECTRIC STARTERS AND ALTERNATORS20 REWIND STARTERS20 COMPONENTS20 ROPE SERVICE 20 STYLIZED REWIND STARTER 21 VERTICAL PULL STARTER HORIZONTAL ENGAGEMENT TYPE 22 STYLIZED REWIND STARTER WITH PLASTIC RETAINER 23 VERTICAL PULL STARTER, VERTICAL ENGAGEMENT TYPE 24 REWIND STARTER MOUNTED IN HOUSING 25 ELECTRIC STARTERS 26 DRIVE ASSEMBLY SERVICE 26 STARTER CHECKING AND SERVICE 27 CHECK FIELD27 ARMATURE CHECK27 TROUBLESHOOTING STARTERS 27 ALTERNATORS 28 CHECKING THE SYSTEM 28 FLYWHEEL (INSIDE-EDGE) BRAKE SYSTEM 29 INSIDE EDGE SYSTEM 29 COMPONENTS29 SERVICE 29 CONTROL CABLE 30 GENERAL INFORMATION 1 ENGINE IDENTIFICATION1 INTERPRETATION OF MODEL NUMBER 1 ENGINE CARE 2 SHORT BLOCKS 2 STORAGE: 2 TUNE-UP PROCEDURE 3 EXHAUST PORT CLEANING 3 2-CYCLE THEORY OF OPERATION 4 OPERATION OF PISTON PORT STYLE 4 OPERATION OF REED PORTED STYLE WITH LOOP SCAVENGING4 TERMS 4 EXHAUST OR SCAVENGE PHASE 4 PORTS 4 EXHAUST PORTS 4 THIRD PORT 4 REED VALVE 4 LUBRICATION 4 AIR CLEANERS, CARBURETORS, GOVERNORS AND LINKAGE 5 AIR CLEANERS 5 POLYURETHANE-TYPE AIR CLEANER 5 KLEEN-AIRE® SYSTEM 5 PAPER-TYPE AIR CLEANER SERVICE 5 GENERAL CARBURETOR INFORMATION 6 CARBURETOR IDENTIFICATION 6 FLOAT-TYPE CARBURETORS 6 DIAPHRAGM (PRESSURE DIFFERENTIAL) CARBURETORS 6 OPERATION7 CARBURETOR SERVICE 7 THROTTLE7 CHOKE 8 ADJUSTING SCREWS 8 FUEL BOWL RETAINING NUT 8 CARBURETOR VENTING 8 HIGH TILT FLOAT STYLE 8 FUEL BOWL 8 FLOAT 8 INLET NEEDLE AND SEAT (FLOAT CARBURETORS) 9 NEEDLE AND SEAT OPO-OFF TEST 9 FLOAT HEIGHT SETTINGS 9 PRIMER BULB 10 CLEANING CARBURETOR BODY10 DIAPHRAGMS 10 INLET NEEDLE AND SEAT 11 FUEL INLET FITTING11 IGNITION 31 IGNITION OPERATION (Pre- 1985 Production) 31 MAGNETO IGNITION 31 CONTACT POINTS 31 CONDENSER 31 OPERATION OF THE TECUMSEH MAGNETO IGNITION 31 SOLID STATE IGNITION (1985 to Present32 SOLID STATE IGNITION OPERATION 32 IGNITION SERVICE 33 SPARK PLUG SERVICE 33 FLYWHEEL REMOVAL AND SERVICE33 FLYWHEEL MAGNETS 33 FLYWHEEL KEYS34 ADAPTER KEY TO FLYWHEEL ASSEMBLY34 FLYWHEEL SLEEVE 34 FLYWHEEL TORQUE34 REPLACING MAGNETO BREAKER POINTS . 34 CONDENSER CHECK IGNITION COIL 34 IGNITION TIMING 34 FIXED TIME SPEED (EXTERNAL COIL) 36 SOLID STATE (CDI) 36 OTHER IGNITION SYSTEMS 36 OUTBOARD TIMING 38 OUTBOARD TIMING (STANDARD IGNITION) 38 OUTBOARD TIMING (SOLID STATE) 39 CYLINDERS & INTERNAL COMPONENTS41 PISTON & RING SERVICE 41 CONNECTING ROD SERVICE 42 NEEDLE BEARINGS 42 CRANKSHAFT, BEARING AND OIL SEAL SERVICE 43 NEEDLE BEARINGS OIL SEALS 43 ONE PIECE SEALS 43 THREE PIECE SEALS 44 OUTBOARD SEAL SERVICE 44 CYLINDERS, REEDS & COMPRESSION RELEASE45 CYLINDER & HEAD SERVICE 45 GASKETS45 REED VALVES 45 AUTOMATIC COMPRESSION RELEASE (DOUBLE REED TYPE) 45 AUTOMATIC COMPRESSION RELEASE (SINGLE REED TYPE45 CYLINDER EXHAUST PORTS 46 TROUBLESHOOTING47 ENGINE FAILS TO START OR STARTS WITH DIFFICULTY 47 ENGINE KNOCKS 47 ENGINE MISSES UNDER LOAD 48 ENGINE LACKS POWER48 ENGINE OVERHEATS 48 ENGINE SURGES OR RUNS UNEVENLY 49 ENGINE VIBRATES EXCESSIVELY 49 SPECIFICATIONS 50 ENGINE TYPE NUMBER AND LETTER REFERENCE 50 SEARS CRAFTSMAN CROSS REFERENCE 51 TABLE OF SPECIFICATIONS 52 - 61 TABLE OF TORQUE LIMITS 62 EDUCATIONAL MATERIALS AND TOOLS 63 AVAILABLE TECHNICIAN'S HANDBOOKS 63 AVAILABLE FOREIGN TECHNICIAN'S HANDBOOKS 63 TOOL KIT 670195D 64 TOOLS65 So as you can see it covers all you need to know, BUT best of all its the cheapest ;-)