1986 Yamaha YZ80 Repair Manual (P/N LIT-11626-05-14)

Get right to work with the 134-page PDF of Yamaha's OEM Owner's Service Manual for the 1986 YZ80S. It covers the 82 cc water-cooled two-stroke engine, six-speed transmission, cooling system, chassis, and CDI ignition. Because the factory procedures are concise and rely on measuring equipment and model-specific service tools, this manual is suited to mechanics and experienced owners who already understand basic motorcycle repair practice.

• Exact YZ80S identification: Yamaha Literature No. LIT-11626-05-14 covers I.B.M. No. 1LR, vehicle I.D. pattern *JYA1LR00GC000101, engine starting number 1LR-000101, and the Mikuni carburetor I.D. mark 1LR00**.
• Engine and bottom-end repair: Details cylinder-head, cylinder, piston, clutch, kick-starter, shifter, CDI magneto, engine removal, crankcase separation, crankshaft installation, transmission inspection, and crankcase assembly.
• Fuel, induction, and cooling: Includes Mikuni VM26 carburetor removal and overhaul, main-jet replacement, float inspection and adjustment, Y.E.I.S. and reed-valve checks, water-pump inspection, and radiator pressure testing.
• Wheels and brakes: Covers wheel removal and installation, spokes, hubs, sprockets and drive chain, rear drum-brake inspection, front brake-pad replacement, caliper and master-cylinder service, disc inspection, and hydraulic bleeding.
• Suspension and steering: Provides fork-oil service, fork removal and disassembly, damper inspection and seal replacement, steering-head service, swingarm and linkage inspection, plus Monocross “De Carbon” shock setup and removal.
• Diagnostics and reference data: Supplies a CDI wiring diagram, ignition fault-isolation chart, cable-routing views, system troubleshooting tables, component torque tables, capacities, clearances, wear limits, and electrical test specifications.

Engine Maintenance, Induction & Bottom-End Repair

Top-end coverage takes the mechanic from cylinder-head and cylinder removal through carbon cleanup, warpage and bore checks, piston and ring measurement, and reassembly. Separate sections address the Yamaha Energy Induction System (Y.E.I.S.), reed-valve sealing and stopper inspection, exhaust maintenance, water pump, wet multi-disc clutch, kick starter, and external shift mechanism.

For a full bottom-end repair, the manual explains engine removal and mounting, case splitting, bearing and oil-seal inspection, transmission and shift-fork removal, gear and shaft checks, crankshaft measurement, and crankcase assembly. The piston-crown arrow must face forward, while the reed and stopper plates use a specific lower-corner orientation; gradual tightening prevents those plates from warping.

The Mikuni VM26 section includes standard jetting, a tuning-and-repair-parts table, main-jet replacement, complete carburetor disassembly and inspection, and float-height adjustment. It does not provide full track-condition jetting theory; detailed carburetor tuning is assigned to Yamaha's separate Race Preparation and Tuning Manual.

Cooling-system coverage includes coolant draining and refilling, water-pump inspection, radiator removal, core and hose checks, radiator-cap testing, and a complete system pressure test. Electrical diagnosis goes beyond the schematic: the ignition flowchart isolates the engine stop switch, spark plug, CDI magneto charge and pickup coils, connectors, ignition coil, and CDI unit. The appendix adds symptom tables for hard starting, poor high-speed performance, overheating, coolant loss, transmission and shifter faults, clutch trouble, and chassis problems.

Chassis, Brakes & Suspension Setup

Chassis repair goes well beyond routine adjustment. The front disc-brake chapter covers pad replacement, caliper piston and seal work, master-cylinder disassembly, hose and disc inspection, and air bleeding. The rear drum brake, wheel bearings and runout, spoke tension, sprocket wear, chain service, steering bearings, swingarm, relay arm, and connecting rod receive their own inspection or repair procedures.

The fork chapter covers oil replacement, removal, complete disassembly, damper-rod inspection, slide-metal removal, seal installation, and reassembly. The Monocross “De Carbon” section provides spring choices, preload and rebound ranges, nitrogen-pressure specifications, handling cautions, and shock removal and installation, but not an internal shock rebuild; shock disposal is expressly marked for Yamaha dealers only. Detailed fork and rear-shock tuning is again referred to the separate racing manual. Yamaha warns that bottoming the inner fork tube during slide-metal removal can damage the oil-lock piece; release fork air pressure before opening the legs, and never open or disassemble the high-pressure shock reservoir.

Factory Tools, Diagrams & Specifications

Named Yamaha tools include the clutch holding tool YM-91042, crankcase separating tool YU-01135, crank installer pot YU-90050 with adapter YM-90063, magneto puller YM-01189, pocket tester YU-03112, fork damper tools YM-01326/YM-33256, and fork-seal driver set YM-33963/YM-01368.

Illustrated references include the CDI ignition wiring diagram, no-spark diagnostic flowchart, ignition-advance curve, transmission-and-shifter exploded view, front-fork exploded view, and cable-routing diagrams for the throttle, clutch, front brake hose, Y.E.I.S. hose, rear-suspension sub-tank hose, and CDI leads.