2002 John Deere Z-Trak F620, F680, F687 Service Manual (P/N TM1678)

• Official John Deere Technical Manual TM1678, June 2002 - a 366-page PDF covering the Z-Trak F620, F680, and F687.
• Engine coverage separates the Kohler CH20S and CH23S configurations and includes leakdown, crankcase vacuum, fuel flow, oil pressure, and ignition testing, followed by carburetor and internal engine repair.
• Model-specific electrical schematics and harness views support diagnosis of the power, cranking, run, charging, PTO/MCS clutch, hour meter, oil-pressure warning, fuel gauge, and optional headlight circuits.
• Hydrostatic power-train content covers zero-creep and tracking adjustment, pump flow testing, control linkage service, hydraulic pump overhaul, and wheel-motor repair.
• Brake procedures distinguish the disc- and drum-type systems, with troubleshooting, park brake adjustment, serial-specific linkage coverage, and component repair.
• Attachment sections cover 48-, 54-, and 60-inch mower decks, including leveling, rotate-to-service and belt adjustments, deck removal, drive shaft and gearbox repair, blade and spindle service, and serial-specific hardware.

John Deere states that this manual is written for an experienced technician. That matches the depth of the material: many procedures require pressure and flow test equipment, electrical meters, pullers, presses, and established engine-rebuilding skills. The F620 and F680 specifications identify the 20 hp Kohler CH20S, while the F687 uses the 23 hp CH23S. This is a technical repair manual rather than an operator's handbook or a full parts catalog.

Variant and Serial-Number Coverage

The serial breaks are important when choosing parts and procedures. Carburetor disassembly is split at engine S.N. 904680/904681 for the F620 and F680, with the later design grouped with the F687. The 48- and 54-inch deck procedures separate units through deck S.N. 015000 from S.N. 015001 and later; 60-inch deck coverage is identified separately as all serial numbers.

Brake coverage also changes by build. The specifications identify disc-type park brakes on the F620 and F680 through S.N. 011536, then drum-type brakes on the F680 from S.N. 011537 and on the F687. Separate F620 park-brake linkage procedures divide at S.N. 016339/016340. The control-lever repair section groups the F620 with the F680 through S.N. 020000; a separate procedure covers F680 S.N. 020001 and later with the F687.

Factory Repair and Diagnostic Depth

The engine section reaches well past routine tune-up work. It documents engine removal, carburetor inspection and assembly, ignition-module testing and air-gap adjustment, cylinder-head and valve reconditioning, governor service, camshaft inspection, hydraulic-lifter priming and bleeding, piston and connecting-rod work, crankshaft inspection and regrinding data, cylinder-block deglazing or reboring, and starting-motor overhaul.

Hydrostatic coverage explains the closed-loop system before moving into fault isolation for loss of pressure, poor tracking, low speed, failure to move, erratic operation, load-related sluggishness, and noise. Pump and wheel-motor chapters include removal, disassembly, inspection, seal and bearing work, reassembly, and related test specifications. Mower repair extends into two serial-specific gearbox designs and two spindle constructions, rather than stopping at belt replacement and deck leveling.

Named visual references include the Engine and Fuel System Troubleshooting Chart, separate F620 and F680/F687 Electrical Schematics, W1 main harness views, the Hydraulic System Schematic, disc- and drum-brake operation views, and serial-specific gearbox and spindle section views.

Specifications, Tools, and Repair Cautions

The specification material includes general and component-specific torque tables, hydraulic flow and pressure test data, fluid capacities and approved lubricants, inspection limits, wear and clearance data, adjustment specifications, and electrical test values. Fuel and lubricant guidance is provided for both North American and European service applications.

Special-tool listings identify equipment by number and use, including the JT03502 cylinder leakdown kit, JT07262 oil-pressure kit, D01169AA in-line hydraulic tester, JT05469 hydraulic flowmeter kit, JDG1240/JDG1241 pullers, JSG777 terminal-removal tool, and AM130907 blade-height gauge.

The repair text also calls out assembly mistakes that can damage parts. For example, forcing a misaligned hydrostatic pump end cover can ruin the end-cover and cylinder-block sealing surfaces, while clamping the hex end of a mower spindle shaft in a vise can damage the shaft and cause improper blade operation.

Before service work begins, the manual's machine-specific safety material should be followed for stored hydraulic pressure, supported raised equipment, rotating components, fuel, batteries, and electrical isolation.