1970s BMW R 60/6 / R 75/6 / R 90/6 / R 90 S Factory Service Manual

Covers 1970s BMW R 60/6, R 75/6, R 90/6, and R 90 S motorcycles equipped with the /6 series boxer engines. This BMW factory service manual features technical data, torque specifications, and service sequences.

Supplied as a single 186-page PDF in English, with a multilingual section index.

• Engine repair: Cylinder-head disassembly and valve grinding, crankshaft and bearing replacement, timing-chain renewal, oil-pump inspection, and valve-clearance adjustment.

• Fuel system: Bing and Dellorto carburetor cleaning, float-level checks, idle-mixture adjustment, throttle synchronization, and choke service for the different configurations.

• Electrical diagnosis: Ignition timing, Bosch alternator and starter overhaul, regulator and diode tests, and separate starter and alternator fault-finding charts.

• Transmission and final drive: Dry-clutch inspection, five-speed gearbox repair, shaft-endplay adjustment, drive-shaft removal, and crown-wheel and pinion setup.

• Chassis and brakes: Telescopic-fork overhaul, steering adjustment, swingarm and wheel-bearing service, drum-brake adjustment, disc-pad alignment, and hydraulic brake bleeding.

• Technical references: Wiring diagram with cable-color key, compression-test graph, cylinder-head tightening-sequence drawing, and component-specific torque, capacity, clearance, and wear-limit tables.

This manual is suited to experienced mechanics with precision measuring equipment and access to the BMW fixtures and pullers specified for internal repair work.

Boxer Engine Repair and Specifications

Engine removal and installation are backed by cylinder boring and honing, valve-guide and valve-seat replacement, and crankshaft endplay adjustment. It provides tolerances for crankshaft main bearing journals, connecting rod clearances, and piston ring sizing, with separate piston fitting clearance and valve timing tables.

The cylinder-head section uses assembly jig BMW No. 5034 for valve work. Timing-drive instructions cover the duplex chain, sprockets, and tensioner, with a specific warning about damage to chain rivet studs during sprocket removal.

The manual includes tightening torques and preload forces tables with metric and imperial units. The reference sheets distinguish BMW N 600 02.0 for general fasteners from BMW N 113 49.0 for self-locking nuts; component sections give their own torque requirements and cylinder-head tightening sequence.

Bing and Dellorto Carburetor Service

The R 60/6 uses Bing slide-type carburetors; the R 75/6 and R 90/6 use Bing constant-depression units. The R 90 S has Dellorto PHM 38 BS/BD slide-type carburetors with accelerator pumps.

Separate adjustment instructions distinguish these systems, including throttle-cable balance and left/right choke-chamber identification. Fuel-tank and line information, air-filter replacement, and exhaust-system removal are also covered.

Bosch Charging, Starting, and Ignition

The electrical section maps out the Bosch alternator and starter system. The charging-system quick test helps distinguish a regulator fault from an alternator fault before replacement parts are selected. Deeper diagnosis covers stator and rotor windings, resistance measurements, and positive, negative, and energizer diodes.

Starter repair includes in-place testing, disassembly, carbon-brush replacement, and armature and field-winding checks. Ignition coverage includes contact-breaker points, centrifugal advance, and timing checks using a test lamp or strobe.

The vehicle wiring diagram and its key identify cable colors, terminals, relays, warning lamps, and grounds. The key distinguishes the R 90 S clock and voltmeter from optional installations on other models. Instruments, lights, and their removal procedures have separate sections.

Five-Speed Gearbox, Clutch, and Rear Drive

Gearbox coverage extends beyond removal and installation to the gear train, selector forks, selector discs, kick starter, and bearing-shim calculations. Transmission-ratio tables accompany the repair sections.

The single-plate dry clutch has diaphragm-spring and driven-plate inspection data. Rear-drive procedures explain matched crown-wheel/pinion identification, backlash measurement, tooth-contact-pattern checks, and shim selection. Drive-shaft and swingarm-bearing work are covered separately.

Forks, Brake Variants, and Chassis

Brake data distinguish the R 60/6 front drum, the R 75/6 and R 90/6 single front disc, and the R 90 S twin-disc arrangement. Procedures cover floating-caliper alignment, master-cylinder removal, bleeding, and mechanical brake adjustment.

Chassis work includes fork alignment checks, steering bearings, rear spring struts, wheel-bearing preload, spoke replacement, and static wheel balancing. Frame data, wheels and tires, foot controls, stands, fenders, and the dual seat are also covered.

Brake and suspension work requires the manual's safety precautions, including its warning against straightening bent fork tubes.

File Format and Readability

The total includes 179 pages from the engine through lighting sections, three opening engine-data pages repeated later, one multilingual section index, and three fastener-reference sheets. Repeated tables and the annotated tightening-sequence sheet are included in the page count.

Text search and navigation: No embedded searchable text or PDF bookmarks; navigation relies on the printed section indexes and page references.

Wiring readability: Cable-color labels benefit from zooming, but some small terminal and instrument-connector markings remain difficult to read. A duplicated cylinder-head page is partially cropped, and some tables require rotation for comfortable reading.