1974–1977 Suzuki GT125 Service & Repair Manual (Pitman Bikebook)

The Pitman Bikebook of the Suzuki GT 125, by John Thorpe and Chris Webb, is an independent maintenance, service, and repair guide for the 1974–1977 Suzuki GT125 two-stroke twin. Its Databank distinguishes A, L, and M versions where carburetor jetting and transmission specifications differ.

• Engine repair: Engine removal, decarbonizing, crankcase separation, piston and bearing inspection, and crankshaft removal, supported by numbered photographic sequences.

• Clutch and transmission: Clutch disassembly, gear-selector linkage service, drive-shaft gear removal, kickstarter work, and gear-engagement checks.

• Carburetors and lubrication: Air-filter service, Mikuni carburetor cleaning and float checks, throttle-slide synchronization, and oil-pump cable adjustment.

• Brakes and running gear: Front disc-pad replacement and bleeding, rear drum-brake service, wheel-bearing replacement, chain adjustment, and fork-oil changes.

• Ignition and fault tracing: Contact-breaker adjustment, dial-gauge timing, a wiring diagram, and symptom-based fault charts for engine, electrical, and chassis problems.

Suited to hands-on owners, the guide explains workshop basics, while its engine strip-down work requires suitable holding tools, pullers, and measuring equipment.

Engine Strip-Down and Transmission Limits

The engine strip-down sequence reaches the alternator stator and rotor, oil-pump and tachometer drives, selector drum and forks, and crankshaft main bearings. Numbered photographs show component positions, while the text explains inspection, alignment, and reassembly details.

Press-work limits: Crankshaft bearing and seal replacement is assigned to a specialist with a hydraulic press. Most of the countershaft gear cluster is also press-assembled; the book recommends assembly replacement for damaged gears, while the separate drive-shaft gears can be dismantled.

The clutch section warns that wedging a screwdriver between the basket and center can damage the fragile basket. Tool coverage includes a clutch holder, rotor puller, impact driver, and vernier caliper.

The crankcase reassembly section identifies Suzuki liquid gasket, part No. 99000-31010.

Fuel, Lubrication, and Brake Service

Fuel supply and oil metering: The diaphragm fuel tap has no conventional off position, and the book distinguishes its vacuum connection from the fuel lines. That distinction helps check fuel delivery before blaming carburetor jetting.

Throttle-slide synchronization is tied to oil-pump adjustment. The carburetor chapter also explains float-valve inspection, starter-plunger service, and air-filter cleaning.

Brake and wheel service: Front-brake coverage centers on pad replacement, slider seals and O-rings, caliper reassembly, and hydraulic bleeding. Rear-brake work includes shoe replacement, cam lubrication, and wear-indicator alignment.

Using unsuitable fluid in the front brake can swell its hydraulic seals and cause loss of braking, a specific warning in the routine-maintenance discussion.

The final-drive section shows rear-wheel removal without disturbing the chain and sprocket, plus cush-drive rubber and wheel-bearing checks. Steering-head bearing adjustment is covered alongside front-fork oil changes.

Fuel and electrical work carries fire and shock risks; review the opening safety chapter and tool-handling advice before starting.

Fault Tracing and Assembly Drawings

Ignition and running faults: The timing section distinguishes approximate rotor marks from final dial-gauge adjustment using a test lamp or buzzer. Fault charts link checks, observed faults, and possible causes for starting problems, uneven running, excessive smoke, clutch trouble, and missed shifts.

Separate charts address steering, suspension, and braking complaints. The electrical discussion explains open- and short-circuit tracing with a test lamp.

Illustrated references include the drive-shaft gear layout (Fig. 50), kickstarter assembly (Fig. 56), selector-mechanism exploded view (Fig. 68), and carburetor components (Fig. 70). A wiring diagram (Fig. 86) accompanies the circuit-tracing discussion.

A Preview of Gearbox, Ignition, and Fork Specifications

These examples are a small selection of the book’s adjustment and fluid-capacity data.

The gearbox capacity is listed as 800 cc for A models and 900 cc for L and M models. The contact-breaker specification is 0.3–0.4 mm for both sets of points.

The front-fork section specifies 125 cc of SAE 10W/30 oil per leg, alongside the oil-change procedure and steering-head adjustment instructions.

Printable PDF, Navigation, and Drawing Detail

Search, navigation, and drawing detail: PDF text search and embedded bookmarks are unavailable. Small wiring labels require zooming, and some switch markings remain blurry when enlarged. Some right-edge detail in the selector drawing (Fig. 68) is cropped.

Supplied as one printable, 80-page PDF in English. The total includes four preliminary pages—cover, title page, contents, and preface—plus 76 numbered pages.