1970–1973 Triumph 650cc Twin T120R/TR6R/TR6C Models Workshop Manual (OEM)

• Official Triumph Engineering Co. Ltd. publication (Part No. 99-0947, 1972 first edition) covering the 1970–1973 T120R Bonneville, TR6R Tiger, and TR6C Trophy.
• Documents both 4-speed and 5-speed transmission configurations, highlighting the transition to early 70s US-market specifications.
• Contains 213 pages of exact technical specifications, maintenance intervals, and exploded-view mechanical diagrams.
• Details the primary chaincase, steering head races, swinging fork, alternator stator, ignition rotor, oil pressure release valve, kickstart mechanism, and tachometer drive.
• Covers the oil pump assembly, auto advance unit, gearchange mechanism, mainshaft bearings, layshaft bearings, tappet guide blocks, valve timing pinions, and gearbox sprocket.

Technical Documentation and Content

The 1970–1973 Triumph 650cc twin PDF workshop manual provides essential bench reference material for servicing and repair on the T120R and TR6 series. This factory publication fully details the unit-construction engine architecture. It outlines diagnostic and mechanical procedures for the crankcase, the forged two-throw crankshaft, and valve timing. The manual also breaks down the entire dry-sump lubrication system. Additional chapters cover tuning the concentric Amal carburetors, setting ignition timing for the contact breaker mechanism, and adjusting the transmission components, including the multi-plate clutch and shock-absorber unit.

Mechanics will find comprehensive step-by-step instructions for tasks that typically require an expensive specialized shop. These include the check procedure for wet sumping, stripping and reassembling the crankshaft assembly, re-seating the valves, renewing mainshaft bearings, setting ignition timing by stroboscope, and clutch and engine sprocket alignment. Having these exact factory tolerances and stripping procedures directly at the workbench prevents costly assembly errors and eliminates trial-and-error troubleshooting, significantly reducing turnaround time for complex engine tear-downs.

For the chassis, mechanics will find detailed frame and attachment data alongside scheduled maintenance for telescopic forks and wheel bearings. Exploded diagrams offer clear visual context for the engine, gearbox, clutch assembly, and exhaust routing. Alongside the essential factory wiring diagrams, technicians will also utilize the engine lubrication diagram, an exploded view of the 650 c.c. engine gearbox unit, a detailed section through the primary chaincase, a plan of gearbox components, an exploded view of the carburetor, and a comprehensive lubrication chart. Understanding these original factory layouts is vital for accurate diagnostics on classic air-cooled British motorcycles. Always cross-reference these original procedures and ensure you have the proper technical background before beginning hands-on work, as vintage motorcycles require precise mechanical handling to operate safely.

Specification Highlights

Factory technical sections deliver the required torque values, clearances, and fluid capacities specifically for the 650cc twin platform. The engine assembly data specifies a flywheel bolt torque of 33 ft·lbs (4.6 kg·m). Outer cylinder head bolts require 18 ft·lbs (2.49 kg·m). The fuel tank capacity is 3 imperial gallons, while the recommended oil reservoir capacity is 4 imperial pints.

Clearances are equally precise. The intake valve clearance is listed at 0.002 inches. Piston ring gap is set between 0.010 and 0.014 inches. Final-stage ignition timing maps at 38° B.T.D.C. All specifications reflect the original factory engineering data for these specific models, ensuring historical accuracy for rebuilds and restorations.