Yamaha YFM400FAR Service Manual

Also see for YFM400FAR: Owner's manual Service manual Assembly manual

Contents

3 - 22CHKADJMEASURING THE COMPRESSION PRESSURE7.Measure: Compression pressureAbove the maximum pressure:Check the cylinder head, valve surfaces, andpiston crown for carbon deposits.Below the minimum pressure:Squirt a few drops of oil into the affectedcylinder and measure again. Refer to the table below.*****************************************************Measurement steps: Crank over the engine with the electricstarter (be sure the battery is fully charged)with the throttle wide-open until thecompression reading on the gaugestabilizes.WARNINGWhen cranking the engine, ground thespark plug lead to prevent sparking.*****************************************************Compression pressure(with oil introduced into cylinder)Reading DiagnosisHigher thanwithout oil Worn or damaged pistonsSame aswithout oilDefective ring(s), valves,cylinder head gasket orpiston is possible.Compression pressure(at sea level):Standard:1,400 kPa (14 kg/cm2 , 203 psi)Minimum:1,218 kPa (12.2 kg/cm2 , 177 psi)Maximum:1,568 kPa (15.7 kg/cm2 , 227 psi)8.Install: Spark plug9.Remove: Fuel tank side panel (right) SeatRefer to “SEAT, CARRIERS, FENDERSAND FUEL TANK”.T R..18 Nm (1.8 m • kg, 13 ft • lb)