1956–1962 Triumph Speed Twin (5T), Thunderbird (6T), Tiger 100, Tiger 110, Trophy TR5, Trophy TR6 & Bonneville T120 Workshop Manual (PN 99–0837)

Triumph Engineering’s Instruction Manual No. 17, Ref. 99-0837, reprinted in November 1973, covers the 1956–1962 Triumph Speed Twin (5T), Thunderbird (6T), Tiger 100 (T100), Tiger 110 (T110), Trophy TR5, Trophy TR6, and Bonneville T120.

Bookmarks and wiring detail: Embedded PDF bookmarks link to technical data, repair sections, and indexes. The manual text is not searchable. Small wiring labels require magnification, and some terminal numbers in the 5T/6T switch diagrams remain faint.

• Engine repair: Engine removal and installation, cylinder-head service, crankshaft and connecting-rod overhaul, valve timing, and dry-sump lubrication diagnosis.

• Gearbox and clutch: Gearbox disassembly, gear-selection troubleshooting, Slickshift adjustment, multi-plate clutch inspection, and clutch shock-absorber service.

• Carburetor service: Amal Monobloc maintenance, Bonneville twin-carburetor synchronization, and S.U. M.C.2 tuning, jet centering, and fault diagnosis.

• Forks and rear suspension: Earlier and later telescopic-fork overhaul, steering-bearing adjustment, swinging-fork pivot inspection, and Girling spring replacement.

• Wheels, brakes, and chains: Standard and Q.D. rear-wheel service, internal-expanding brake repair, Dunlop tire fitting, and Renold chain lubrication and link repair.

• Lucas electrical systems: Dynamo and alternator wiring diagrams, magneto and coil-ignition timing, contact-breaker service, and starting or misfire diagnosis.

Triumph wrote this manual for owners servicing their motorcycles, while advising inexperienced owners to leave major engine, fork, and gearbox repairs to a dealer with the necessary workshop equipment and special tools.

Engine Overhaul and Valve Timing

Engine repair coverage runs from crankcase separation to cylinder-head preparation, bearing inspection, and crankshaft and connecting-rod assembly. Decarbonizing is described with the cylinder block left in place; separate sections address one-piece crankshaft balancing and earlier two-piece crankshaft assembly.

The dry-sump lubrication section explains the twin-plunger oil pump, pressure relief valve, and scavenging circuit, supported by an engine lubrication diagram. Engine procedures identify camwheel tool Z89 and crankshaft-pinion extractor Z121.

Valve-timing diagrams and the identifying mark beside the engine number distinguish ramp-cam configurations from high-lift camshafts. This helps owners select the appropriate tappet data; the manual explains how insufficient ramp-cam clearance can lead to burned valves.

Gearbox, Slickshift, and Clutch Service

Gearbox references cover the positive-stop selection mechanism, camplate inspection, and standard, wide-ratio, and close-ratio gear sets. The Bonneville T120 has a similar gearbox without Slickshift.

Gearbox component views and the clutch and shock absorber exploded view have numbered component keys. Clutch inspection covers friction plates, springs, rollers, and drive rubbers. Slickshift adjustment notes explain how incorrect adjustment can leave the clutch slipping and accelerate friction-material wear.

Coverage of the Smith’s speedometer installation includes its gearbox drive and cable; internal instrument overhaul is outside this manual’s scope.

Amal Monobloc and S.U. Carburetor Diagnosis

Amal coverage addresses flooding, mounting-flange distortion, and fuel-metering components. Bonneville procedures cover simultaneous throttle-slide operation and float-chamber height as part of twin-carburetor setup.

S.U. M.C.2 component views accompany diagnosis of sticking pistons, off-center jets, air leaks, and fuel leakage. The fault-finding section also distinguishes carburetor problems from compression and ignition faults.

Fuel-system service requires a ventilated workspace free of ignition sources.

Telescopic Forks, Girling Units, and Wheel Service

Separate procedures and exploded views cover earlier and later telescopic forks, including bush and seal replacement, alignment, and spring identification for solo and sidecar use. Swinging-fork coverage describes pivot construction, bush wear, clearance shims, and the access needed for replacement.

Girling SB4 coverage includes spring removal, spring-preload adjustment, and damper checks. The sealed hydraulic damper units are assigned to specialist servicing rather than internal rebuilding in this manual.

Wheel chapters distinguish full-width front hubs from earlier detachable brake-drum arrangements. Standard and quickly detachable rear wheels have separate service instructions, including the Q.D. arrangement that allows wheel removal without disconnecting the chain or rear brake.

Lucas Wiring and Ignition Fault Finding

Electrical coverage distinguishes dynamo-equipped machines from Lucas RM14, RM13/15, and RM15 alternator systems. Wiring diagrams show dynamo installations, 5T/6T circuits, and later T110/TR6/T120 arrangements.

Magneto maintenance covers lubrication, contact-breaker adjustment, high-tension pickups, and cables. Coil-ignition diagnosis includes distributor, coil, and condenser checks, with separate fault descriptions for normal and emergency ignition-switch positions.

Maintenance Schedules and Troubleshooting Charts

Maintenance tables cover oil changes, chain tension, and steering-head lubrication. The reference section also contains lubricant charts, gearing/RPM charts, and fault-finding tables for starting trouble, stalling, misfiring, power loss, and overheating.

Piston Ring, Oil Tank, and Ignition Specifications

The piston-service data specify a new compression-ring end gap of 0.010–0.014 in (0.25–0.35 mm), with separate scraper-ring figures for the different engine sizes.

The oil-tank capacity is listed as 5 pints (3 liters). The primary chaincase has a separate oil-capacity specification.

Bonneville T120 ignition data specify 39° before T.D.C. with the magneto fully advanced, distinguishing the timing figure from a retarded setting.

Printable PDF and Included Pages

Supplied as one printable English-language PDF with 194 pages total: the 192-page manual, including its title page and indexes, plus one outer cover and one illustrated supplemental page. Both additional pages are already included in the total.