Yamaha YFM40FB (Big Bear 400) Service Manual (P/N 4S11/4S14)

• 388-page official Yamaha publication (P/N 4S11/4S14), first edition consistent with the 2007–2010 model run
• Covers 2007–2010 Yamaha YFM40FB (Big Bear 400) ATVs equipped with the 387cc SOHC 4-stroke engine, shaft drive, and wet multi-disc braking system
• Details assembly and service parameters, specifically documenting the wet multi-disc rear brake system not found on earlier variants
• Includes 124 exploded-view component diagrams and 44 critical engine/chassis torque specifications tables

Service and Maintenance Documentation

The 2007–2010 Yamaha YFM40FB service manual thoroughly documents procedures for engine, chassis, and electrical system diagnostics. Working on ATVs carries inherent risks, so reviewing factory-approved lifting points and safety precautions before starting any maintenance is essential. General sections detail vehicle identification, distinct features, and the special tool requirements necessary for heavy chassis or engine work. You will find periodic check and adjustment chapters outlining the complete maintenance chart. This covers the emission control system, throttle lever free play, valve clearance, and starter cable adjustments. Further in, detailed chapters break down the carburetor, drive train, and suspension components. The electrical system section provides complete circuit diagrams alongside troubleshooting charts for lighting and starting circuits.

Specifications and Reference Values

Getting the numbers right is critical for high-performance operation. Cylinder head warpage limits are strictly set at 0.05 mm. Valve clearance for the intake is specced at 0.06–0.10 mm in the cold state. Need ignition timing? It is documented at 10°/1,500 r/min. Essential torque specifications include engine oil drain bolts tightened to 32 Nm and cylinder head bolts set at 40 Nm, which follow a multi-stage assembly sequence. Fluid capacities are clearly defined throughout the publication. The engine oil total amount requires 3.5 L, while the final gear oil takes 0.53 L. Standard tire pressure for typical off-road use stands at 22–28 kPa.