1987–1990 Yamaha YFM350ER Moto-4 Four-Wheeler Service Manual

• Complete factory coverage for the 1987–1990 Yamaha YFM350ER Moto-4 featuring the 350 cc oil-cooled engine configuration.
• 310 pages (P/N LIT-11616-06-01) of official OEM schematics, exploded-view diagrams, and accurate factory fastener torque specifications.
• The only workshop edition providing comprehensive assembly and disassembly teardowns for the 350 cc platform drivetrain.
• Features detailed step-by-step coverage for recoil starter rebuilds, CDI rotor disassembly, balancer drive gear servicing, oil pump clearances, secondary clutch inspection, and decompression cam tolerances.
• Includes crucial data on shift cam segment alignment, crankcase separation procedures, rocker arm shaft extraction, valve seat recutting techniques, middle driven gear lash, ignition timing verification, and comprehensive wiring diagrams.

Engine and Chassis Documentation

Whether you are rebuilding the top end or dialing in the carb, this technical manual provides the exact factory procedures for your Moto-4. It details everything from routine periodic adjustments to complete overhauls. You get precise data for the fuel system, including carburetor float level settings and air filter maintenance, right alongside the correct engine and final gear oil capacities. Need to check the automatic cam chain tensioner, valve clearances, or compression pressure on the 350 cc power plant? The exact factory measurements are right here.

The chassis section goes just as deep, walking you through steering system inspections, brake lever and pedal adjustments, and tire pressure management. This ensures you maintain complete OEM service coverage for the entire series. This PDF provides a distinct workshop advantage: you can quickly reference exact valve spring free length and clutch friction plate thickness limits directly at your parts washer, eliminating the risk of reinstalling out-of-spec components during a complex engine repair. The documentation also provides step-by-step instructions for procedures that typically require expensive dealer labor, such as crankcase separation, valve seat recutting, and complete transmission main axle teardowns.

Factory Technical Specifications

Mechanics know that inaccurate tolerances ruin engines. That is why this manual is packed with hard technical data to keep your build accurate and reliable. The engine service tables list cylinder head bolt torque values strictly at 40–50 N·m (29–37 lb-ft), while the cylinder head specification charts put the intake valve clearance precisely at 0.06–0.10 mm (0.002–0.004 in). Electrical troubleshooting is covered down to the exact resistance and fuse ratings for the magneto pick-up coil and related circuitry. Beyond standard text, the content utilizes clear electrical routing drawings, precise valve seat cutting schematics, detailed crankshaft assembly views, and troubleshooting flow charts to guide your workflow.

When working on the YFM350ER, be aware of a common pitfall: incorrectly aligning the balancer gear punch marks with the buffer boss during reassembly will result in severe engine vibration and rapid bearing failure. Additionally, always verify the automatic cam chain tensioner rod for fatigue, as a stuck tensioner is a frequent cause of skipped timing on this specific 350 cc platform.

You will also find clear gear lash measurements to ensure your final drive assembly runs flawlessly. Before turning wrenches on these critical systems, ensure you have the proper tools and mechanical background to work safely, as improper maintenance or relying on incorrect specs can lead to serious equipment damage or injury.