Yamaha Big Wheel 350 / BW350T Service Manual 1987–1988 (P/N LIT-11616-05-69)

• Exact coverage: Identifies the Yamaha BW350T, model code 2JN, from vehicle serial JYA2JN00*HC000101 and engine serial 2JN-000101. The official November 1986 first edition is supplied as a 246-page PDF under Yamaha P/N LIT-11616-05-69.
• Engine and transmission repair: Covers engine removal and remounting; cylinder-head, valve, camshaft, and cam-chain work; cylinder and piston inspection; crankcase separation; crankshaft and balancer service; the oil pump, clutch, kick and electric starters; and constant-mesh transmission and shifter overhaul.
• Carburetor procedures: Details Teikei Y28P removal, full disassembly, passage and jet inspection, float and needle-valve checks, coasting-enricher diaphragm service, reassembly, installation, and float-height and fuel-level adjustment.
• Chassis work: Includes front and rear wheel and drum-brake inspection, fork disassembly and oil service, steering-head bearing service, De Carbon rear-shock handling, and repair of the swingarm, middle sprocket shaft, and primary and secondary drive-chain system.
• Electrical fault finding: Provides the BW350T wiring diagram plus separate circuits and troubleshooting paths for the starting circuit cut-off, CDI ignition, charging, lighting, and neutral-indicator systems, together with starter-motor overhaul.
• Factory reference data: Supplies exploded assemblies, section views, special-tool numbers, component and general torque tables, capacities, wear limits, clearances, pressure data, lubrication diagrams, and cable-routing drawings.

BW350T Coverage and Intended User

This factory service manual is built around the BW350T/2JN configuration: a factory-listed 348 cc, air-cooled SOHC four-stroke single, wet multi-disc clutch, five-speed constant-mesh transmission, and both electric and kick starting. Yamaha states that the book was written primarily for dealers and qualified mechanics and assumes a basic understanding of mechanical repair concepts and procedures. It is a technician-level reference, not a substitute for basic mechanic training.

Engine and Fuel-System Depth

The engine chapter follows the complete workshop sequence from removal and disassembly through inspection, repair, assembly, adjustment, and remounting. It also identifies the clutch, top end, kick starter, shift shaft, CDI magneto, piston and cylinder, camshaft, and valves as serviceable without removing the complete engine.

Inspection coverage includes valve sealing, guide replacement and reaming, valve-seat cutting and lapping, cam and rocker wear, cylinder and piston measurement, piston-ring checks, clutch wear, oil-pump clearance, starter-clutch operation, transmission gear and shift-fork inspection, crankshaft runout, and balancer alignment. The Teikei Y28P carburetor chapter adds a labeled section view and exploded assembly, along with fuel-level measurement using gauge YM-01312 after float adjustment.

Chassis and Electrical Diagnosis

Chassis coverage reflects the BW350T’s unusual dual-chain layout. It documents primary and secondary drive-chain service, the middle sprocket shaft, swingarm inspection, and side-clearance measurement and shimming. Wheel and drum-brake inspection, bearing replacement, wheel balance, fork-damper disassembly, steering-head bearing adjustment, and front-fork oil service are also included.

The De Carbon rear-shock section covers handling, removal, inspection, installation, and disposal; it does not provide an internal damper rebuild. Electrical repair is organized into system-specific fault paths for the starter circuit, CDI ignition, charging, lighting, and neutral signal. Tests cover the related switches, relay, coils, wiring, and charging and lighting output, with fault isolation to the regulator/rectifier. The starter-motor section includes disassembly and checks for the armature, brushes, commutator, mica undercut, seals, and bearings.

Illustrations, Tools, and Shop Data

Diagram support includes the BW350T master wiring diagram, starting-circuit operation chart, ignition and charging circuit diagrams, carburetor section view, engine and transmission exploded assemblies, lubrication diagrams, and cable-routing views. Factory tool references include the Universal Clutch Holder YM-91042, Valve Seat Cutter YM-91043, Fork Damper Rod Holder YM-33256, Pocket Tester YU-03112, and Electro Tester YU-33260.

The appendices consolidate engine, chassis, and electrical specifications with component-specific torque data, capacities, wear limits, adjustment data, and test values. During transmission removal or installation, the drive-axle oil-seal lip is vulnerable to damage. The primary drive-chain O-rings can also be damaged by steam cleaning, high-pressure washing, or solvent-bearing lubricants.

Support the machine securely before wheel, fork, swingarm, shock, or engine work. The pressurized De Carbon rear shock must not be opened or exposed to heat.