1970–1973 Triumph 650cc Twin T120R/TR6R/TR6C Workshop Manual (P/N 99-0947)

Official Triumph Engineering Co. Ltd. workshop publication for the 1970–1973 Triumph 650cc twins: T120R Bonneville, TR6R Tiger, TR6C Trophy, and their T120RV, TR6RV, and TR6CV variants. Publication Part No. 99-0947, published January 1972, covers machines from engine number KE 00001 onward.

Supplied as a 213-page PDF in English.

• Engine repair: Engine removal, crankshaft disassembly and reassembly, valve reseating, piston inspection, and valve timing for the unit-construction, air-cooled twin.

• Lubrication: Dry-sump oil pump service, oil pressure release valve inspection, filter maintenance, and diagnostic checks for wet sumping.

• Fuel and ignition: Amal concentric carburetor overhaul, twin-carburetor synchronization, contact breaker adjustment, and ignition timing with a stroboscope.

• Transmission: Separate 4-speed and 5-speed gearbox procedures, multi-plate clutch repair, shock-absorber unit inspection, and primary chain adjustment.

• Chassis and brakes: Telescopic fork overhaul, steering head races, swinging fork bushes, wheel bearings, twin-leading-shoe front brakes, and rear drum brakes.

• Electrical diagnosis: Ignition fault finding, alternator and rectifier tests, Zener diode checks, lighting service, and wiring diagrams for earlier and later machines.

Written for workshop fitters, technical staff, and owners performing basic maintenance and repair; the manual identifies wheel building as work best left to a specialist.

Engine Repair and Dry-Sump Lubrication

Engine procedures cover crankcase separation, the forged two-throw crankshaft, tappet guide blocks, valve timing pinions, and tachometer drive. The general data distinguishes the timing-side main bearing fitted after engine number GE 27209.

The wet-sumping checks address excessive oil discharge from the breather and smoky exhaust. Scavenge suction tests and return-system checks help distinguish air leaks at the pump or crankcase from restrictions in the oil return or reservoir vent, giving a practical starting point for lubrication diagnosis.

Amal Carburetors, Ignition Timing, and Exhaust

Fuel-system instructions distinguish the single-carburetor TR6 arrangement from the twin-carburetor T120 setup, including synchronization and differences in throttle-cable layouts. Ignition work covers the auto advance unit, contact breaker mechanism, and timing checks using the alternator rotor marks.

Exhaust illustrations show the balanced system used on the T120R and TR6R alongside the separate TR6C arrangement.

Clutch and 4-Speed/5-Speed Gearbox Repair

Separate gearbox chapters cover the gearchange mechanism, kickstart mechanism, mainshaft bearings, layshaft bearings, and gearbox sprocket. The 5-speed instructions specify paired replacement of the high gear and its main roller bearing when either requires renewal.

Primary-drive procedures cover the clutch assembly, shock-absorber rubbers, alternator stator, and clutch and engine sprocket alignment. The manual warns that sprocket misalignment can fracture chain rollers and damage the crankcase, and that overtightening the kickstart ratchet pinion nut can cause its thin-walled steel sleeve to fail.

Frame, Suspension, and Electrical Service

Frame and attachment data extend to control cables, suspension mounting points, fork dampers, and wheel alignment. Rear suspension instructions cover Girling spring and bush work; the sealed hydraulic damper unit is not dismantled for internal repair.

Electrical sections distinguish condenser arrangements around engine number CG 50414 and include the Lucas 2MC capacitor ignition option. Separate wiring diagrams are keyed to engine number HG 30870. Alternator testing is covered, but stator winding repair is outside the manual's scope.

Observe the manual's lifting and support precautions during engine and wheel removal.

Factory Specifications, Diagrams, and Service Tools

Reference data include component-specific torque values, clearances, fluid capacities, piston and cylinder inspection limits, ignition settings, electrical test values, and maintenance intervals. Conversion, drill, wire-gauge, and thread tables support workshop measurements.

Illustrations include the engine lubrication diagram and lubrication chart, an exploded view of the 650cc engine/gearbox unit, a section through the primary chaincase, plans of gearbox components, and an exploded carburetor view.

The service-tool section identifies crankcase parting tool 61-6046 and camwheel extractor 61-6132 for the later camwheels fitted after engine number CG 50464.

File Format and Readability

The 213-page total includes two historical brochure pages, three blank pages, and the cover, title, and printer-imprint pages.

The manual text is not searchable. Its 57 PDF bookmarks provide navigation to major sections and selected subtopics. Small wiring labels and wire-color codes are readable with enlargement; both wiring-diagram pages use rotated layouts.