Yamaha F150B Service Manual

Also see for F150B: Owner's manual Service manual Owner's manual

7-1Power unitPOWRPower unit (check andadjustment)Checking the compression pressure1. Start the engine and warm up until theengine idle speed is stable at 650–750 r/min, and then turn it off.2. Remove the clip from the engine shut-offswitch.3. Disconnect all fuel injector couplers.4. Remove the spark plug wire cover and allspark plugs, and then install the specialservice tools a and b into a spark plughole. NOTICE: Before removing thespark plugs, blow compressed air inthe spark plug well to clear out anydirt or dust that may fall into thecylinder.5. Disconnect the throttle cable joint fromthe accelerator lever c, and then placeand hold the lever in the fully openposition of the throttle.6. Crank the engine until the reading on thecompression gauge stabilizes, and thenmeasure the compression pressure.7. If the compression pressure is belowspecification and the compressionpressure for each cylinder is unbalanced,add a small amount of engine oil to thecylinder, and then measure thecompression pressure again.TIP:• If the compression pressure increases,check the pistons and piston rings. Replaceif worn. See “Assembling the cylinder block”(7-61).• If the compression pressure does notincrease, check the valve clearances,valves, valve seats, cylinder head gasket,and cylinder head. Adjust or replace if nec-essary. See “Cylinder head” (7-36).Compression gauge a:90890-03160Compression gauge extension b:90890-06563baMinimum compression pressure(reference data):880.0 kPa (8.80 kgf/cm 2, 127.6 psi)c