1987–1991 Yamaha Champ YFM100T, YFM100 ATV Service Manual (P/N LIT-11616-05-82)

• A 239-page PDF containing three Yamaha factory publications for the YFM100T, YFM100W, and YFM100A: YFM100T Service Manual P/N LIT-11616-05-82, 186 pages; YFM100W Supplementary Service Manual P/N LIT-11616-06-59, 39 pages; YFM100A Supplementary Service Manual P/N LIT-11616-07-42, 14 pages.
• Covers engine removal and overhaul, from the cylinder head, piston, and centrifugal clutch through the oil pump, starter drive, CDI magneto, four-speed transmission, middle gear, crankshaft, and crankcase.
• Details Mikuni carburetor removal, disassembly, inspection, reassembly, installation, fuel-level and float-height adjustment, plus the factory maintenance and lubrication schedule.
• Explains wheel and drum-brake repair, steering and toe-in adjustment, front-suspension service, and rear-axle/shaft-drive removal, inspection, installation, and operational checks.
• Adds the YFM100W rear swingarm and shock absorber, oil-filled final drive, revised rear-axle hardware, and rear-brake starting interlock, followed by the YFM100A regional identification, specification, throttle, and brake updates.
• Includes YFM100T and YFM100W wiring diagrams, system circuit diagrams, fault-isolation charts, and component tests for the electric starter, CDI ignition, charging, and lighting systems.

This PDF combines Yamaha's original YFM100T service manual with the later YFM100W and YFM100A supplements. All three are first editions, dated September 1986, August 1988, and July 1989. Written primarily for Yamaha dealers and qualified mechanics, the material assumes a basic understanding of mechanical repair and is not a beginner-level repair guide.

Exact Model and Serial Identification

The base manual identifies the YFM100T as model code 2HX, beginning with VIN JYA2HX00HC000101 and engine number 2HX-000101. The YFM100W supplement covers model code 3GB, beginning with VIN JY43GBW0KC000101 for the U.S., Canada, and Australia; its frame and engine numbering begins at 3GB-000101.

For the YFM100A, the supplement separates 3GB3 U.S./Australian machines from 3GB4 Canadian/European machines. It lists JY43GBW0LC027101 for the U.S. and Australia, JY43GBN0LC041101 for Canada, European frame number 3GB-041101, and engine starting numbers 3GB-027101 for the U.S./Australia and 3GB-041101 for Canada/Europe. The W supplement must be used with the T manual, while the A supplement must be used with the W material; all required preceding publications are present in this PDF.

Factory Repair Depth

The engine chapter goes well beyond tune-up work. Inspection and repair coverage spans the valvetrain, cylinder and piston group, centrifugal clutch, lubrication system, crankshaft, four-speed transmission, middle gear, and bearings. Assembly procedures address middle-gear shim selection plus clutch-boss and friction-plate height adjustment. Crankcase sealing and function checks, cam timing, chain-tension setup, and final engine remounting are also documented. The cylinder, cylinder head, and flywheel magneto can be serviced without removing the complete engine.

The chassis material follows the same repair-oriented format for the wheel hubs and drum brakes, steering shaft and tie rods, leading-arm front suspension, rear axle, and shaft drive. The YFM100W supplement is especially important for later 3GB machines because it adds swingarm and rear-shock removal, free-play inspection, installation, cable routing, and revised final-drive service information.

Specifications, Tools, and Diagrams

Factory reference data includes component-specific torque tables, fluid and lubricant capacities, wear limits, clearances, carburetor settings, brake and steering adjustment data, electrical resistance and output specifications, general fastener torques, unit definitions, and conversion tables. Key tool listings include Valve Adjusting Tool YM-08035, Flywheel Puller YM-01189, Clutch Holder YM-91042, Crankcase Separating Tool YU-01135, Pocket Tester YU-03112, and the 3GB Rear Axle Nut Wrench YM-37132/90890-01422.

Named graphics include the YFM100T Wiring Diagram, YFM100W Wiring Diagram, Electrical Starting System Circuit Diagram, Ignition System Circuit Diagram, Carburetor Sectional View, and Lubrication Diagram. Exploded assembly and cable-routing views support parts identification and correct assembly throughout the repair sections.

The crankcase section warns that forcing uneven separation can damage the gasket mating surfaces when a screw or fitting remains. The oil-pump assembly coverage calls out passage pre-lubrication to prevent engine damage at restart; the clutch diagrams also lock down the bent-plate and black/silver friction-plate order. Because these ATVs use low-pressure tires, mechanical drum brakes, an exposed fuel system, and a flooded battery, the manual's warnings and final checks should be followed before the machine is returned to service.