1981 John Deere 650 & 750 Tractors Technical Manual (P/N TM1242)

• 798-page PDF of John Deere Technical Manual TM1242 (01SEP84) in English for 650 and 750 tractors, combining factory repair sections with separate operation-and-test sections.
• Distinguishes the 650 two-cylinder and 750 three-cylinder diesel engines, with repair coverage for the valve train, cylinder head, camshaft, pistons, rods, cylinder block, crankshaft, main bearings, lubrication system, cooling system, fuel injection, governor, and Thermo-Start.
• Separate 650 and 750 chapters document tractor separation and power train repair, including front-end and engine removal, clutch-housing splits, sliding-gear transmissions, rear PTO, differential, final drive, standard-front-axle/non-MFWD configurations, MFWD, and front PTO where equipped.
• Steering, brake, and hydraulic work includes manual steering, field-option power steering, brake assemblies, hydraulic pump repair, rockshaft and 3-point hitch service, main and surge relief valves, selective control valve repair, front axle work, wheels, ROLL-GARD, and seat-belt installation.
• Diagnostic sections cover dynamometer, compression, oil-pressure, and cooling-system tests; clutch, transmission, PTO, final-drive, and oil-leakage isolation; electrical circuit testing and wiring diagrams; front PTO interlock diagnosis; and step-by-step hydraulic flow and pressure diagnosis.
• Factory tool information identifies the JDF-14 timing fixture, JDST-28 belt tension tool, JDG-19 lift eyes, hydraulic flow and pressure testers, and dimensioned fabrication drawings for separate 650 and 750 transmission disassembly stands.

Model-Specific Repair Coverage

This manual does not treat the 650 and 750 as interchangeable. The engine repair chapters separate the two-cylinder 650 from the three-cylinder 750, including model-specific cylinder-head tightening patterns and valve-setting sequences. The power train sections diverge further. The 650 material covers its change-shift lever, reverse-gear shaft, differential-drive shaft, and MFWD outer-drive assemblies. The 750 chapters add the Hi-Lo shifter, separate front and rear differential-drive shaft halves, drop housing, spindle housings, and the related bearing-clearance, drag-torque, and backlash checks. Those distinctions help ensure that the selected teardown procedure, inspection point, and specification table match the tractor on the stand.

The separation coverage is unusually detailed. Separate photo sequences address removal and installation of the front end, engine, clutch housing, transmission, differential, and axle, along with the required blocking, support stands, lift eyes, and transmission stands. Engine repair runs from top-end service through piston, crankshaft, main-bearing, oil-pump, and cooling-system work. Fuel-system coverage includes injection-pump removal and timing, fuel-system bleeding, nozzle opening-pressure, leakage, chatter, and spray-pattern tests, governor repair, precombustion-chamber service, and Thermo-Start diagnosis.

The general section also covers predelivery and after-sale inspection, tune-up, cooling-system service, fan-belt adjustment, injection timing, lubrication points, engine and transmission-hydraulic oil service, filter and screen service, MFWD axle oil, and front PTO bearing service.

Diagnostics, Diagrams, and Factory Data

Operation-and-test sections explain how each system works before moving into fault isolation. Notable visual references include engine lubrication and cooling-flow diagrams, clutch/transmission/PTO power-flow diagrams, the fold-out electrical wiring diagram, the front PTO interlock diagnostic sequence, open-center hydraulic schematics for rockshaft, power-steering, and selective-control-valve configurations, and exploded MFWD assemblies. Electrical coverage includes the alternator, regulator, starting motor, senders, lamps, switches, fuses, and a seven-step probe-light circuit check. Hydraulic diagnosis uses preliminary checks, oil-temperature preparation, flow-meter hookups, pressure testing, and charted results to isolate the pump, relief valves, rockshaft, steering, or selective control valve.

Related tables provide component-specific torques, hydraulic pressure and flow specifications, approved lubricants and fluid capacities, service intervals, wear limits, end play, backlash, clearances, and electrical test values. The tractor is metric by design, and most specifications are paired with U.S. customary equivalents.

Workshop Notes and Scope

The manual calls out repair traps that matter during major teardown. In the MFWD separation procedures, the drive shaft can pull from its splined coupler and both tractor halves must remain correctly supported; elsewhere, the removed engine is not to be rested on the center of its oil pan. The cylinder-head chapter also separates the smaller auxiliary cap screws from the main fasteners so they are not over-tightened.

Tractor separation, suspended cast components, electrical service, and high-pressure hydraulic testing carry serious shop hazards. The manual's blocking, lifting, battery-isolation, pressure-release, and leak-check warnings should be reviewed before repair work begins. This is the factory technical manual for workshop diagnosis and repair, not an operator's manual or parts catalog.