Workshop Walkthrough

Triumph Bonneville unit-construction — four-stage animated walkthrough

A four-stage preview of a Triumph Bonneville unit-construction twin restoration. The teardown stage walks the separated engine / primary-case drain, cam-ring orientation, and the three-stage reverse-torque head lift. The engine stage plays the full procedure on-canvas. The wiring stage previews Lucas electrical work. The reassembly stage ends at the cold tappet set.

Teardown: Drain engine and primary-case lubricant separately on the unit-construction twin, mark the cam-ring orientation to the crankshaft pinion, lift the cylinder head in the three-stage reverse-torque sequence (28 -> 21 -> 14 N-m), and pull the slip joints free before the barrel comes off.

Workshop Walkthrough

Watch each step animated on-canvas, then run the numbered steps below at the bench. Tap to pause; pinch to zoom when paused.

STEP 01

Step 01 - Drain oil and primary-case lubricant separately - the uni...

Drain oil and primary-case lubricant separately - the unit-construction twin shares no sump between engine and primary.

01/8

No video yet? Download the placeholder clip (MP4) — or drop a real workshop recording into the same slot when it's ready.

Family reference

Bonneville (T120/T140)Triumph Bonneville N1Triumph Bonneville S1Triumph Pre-UnitTriumph hub

Loading guide...

Read next

A workshop-grounded walkthrough of scope, tools, time, model choice, and the pitfalls first-time restorers hit hardest — written for the reader who has not yet picked a bike.

Open the getting-started pillar

Read next

Triumph unit-construction 649cc parallel twin (T120R / T120T / T120C, 1963-1972). Factory tolerances by year band (bore 71 mm, stroke 82 mm, 649 cc std; T120C competition head 10.5:1), Lucas E3L 1963-1968 -> Lucas RM15 + WIPAC diode board 1969-on cross-era harness, chassis build-month transition across the 1968-1969 ground-polarity switchover, 1971 twinshock -> Uni-Trax rear suspension, Amal 930 (1963-1968) -> Amal 932 (1969-on) carb size step, and the 14-step Meriden factory concours assembly sequence.

Open the Triumph Bonneville T120 Restoration Guide

Read next

Honda SOHC inline-four (K0–K8), disc-brake era. Factory tolerances, model-specific tools, and sequenced teardown/reassembly for the engine, gearbox, carbs, and electrical harness.

Open the CB750 Restoration Guide

Read next

Harley-Davidson OHV big-twin (1966-1984). 1966-1979 cast-iron head 74"/80" era with concentric rocker arms, the 1980-1984 aluminum head + 1340cc late-Shovel cambio, the 1974+ electronic ignition retrofit, and the H-D bulletin AS-13165 cylinder barrel resurfacing caveat that gates the aluminum-head rebuild.

Open the Harley-Davidson Shovelhead Restoration Guide

Read next

Yamaha 653cc SOHC pushrod vertical twin (1970-1985). Mikuni BS-side carburettor pair, the 1977 shim-under-bucket valve spec refresh, the 1980 TCI electronic ignition transition on the XS650S Special, pushrod cam-chain tensioner service, and three-phase PM alternator charging in negative-earth convention.

Open the Yamaha XS650 Restoration Guide

Read next

BSA DOHC single-cylinder (1938-1963) -- DBD34 rigid-rear (1938-1948), YA / ZA / ZA-B Golden Flash plunger-rear (1949-1958), DBD34GS Clubman swinging-arm (1956-1962), 1959 Catalina scrambler with Lucas RM13 alternator + negative-earth switchover, and B50SS Clubman continuation (1961-1963). DOHC shim-under-bucket wedge spec (I 0.10 / E 0.15 mm), BTH fotQ versus Lucas W2 / W3 stand-alone magneto split, and the 1956 swinging-arm chassis pivot.

Open the BSA Gold Star Restoration Guide

Read next

Norton Commando 750 / 850 unit-construction parallel twin (1967-1977). Isolastic cradle cradle bolt torque bands (Mk1 22-27 N.m single-layer vs Mk2 / Mk3 30-35 N.m sandwich-mount), Atlas-style gearbox retrieval end-float (mainshaft 0.10-0.20 mm / layshaft 0.05-0.15 mm), 12-step factory reassembly sequence from engagement cover through tank, MA12 / RM15 charging crossover at the 1971 Lucar transition, and the Lucas Rita SSI twin-spark aftermarket retrofit for the Mk3 850.

Open the Norton Commando Restoration Guide

Read next

BMW R90S /6 sport flagship boxer-twin (1973-1976, 898cc). Twin-disc front brake (R90S only), Bing 94 slide-carb pair, long-shaft 33/11 final-drive unit, and the 1973/74 mid-model-year ground-polarity switchover from positive to negative earth. Covers the factory contact-breaker points ignition on early 1973 /6 production AND the factory Hella electronic ignition retrofit kit on the late /6 1974-1976 production.

Open the BMW R90S Restoration Guide

Notify me

One email the moment a new model line ships. No newsletter.