Carbon accumulation on piston and in
cylinder head (combustion chamber) is
higher than the
suspected due to damaged valve stem
or piston oil rings.
Incorrect cylinder head gasket
Damaged auto-decompressor spring or
decompressor do not move smoothly.
Exhaust gas leakage around cylinder
lower than the
Incorrect seating surface of valve.
Valve clearance is too narrow.
Piston/cylinder clearance is too wide.
Bad condition of piston ring and/or
piston ring grooves.
Auto-decompressor do not move
Cylinder Head Removal
Fuel Tank (see Fuel Tank Removal in the Fuel System
Camshaft Chain Tensioner (see Camshaft Chain Ten-
Cylinder Head Cover (see Cylinder Head Cover Re-
Camshaft (see Camshaft Removal)
Carburetor (see Carburetor Removal in the Fuel System
Exhaust Pipe [A] (see Muffler Removal)
Clamp Screw [B]
Water Hose [C]
Engine Bracket Bolts [D]
Engine Bracket [E]
Remove the 6 mm cylinder head bolts [A] and loosen the
cylinder bolt [B].
This prevents the 6 mm bolts from becoming damaged.
ENGINE TOP END 5-21
Remove the carbon deposits and replace
damaged parts if necessary.
Replace the gasket with a standard one.
Replace the spring or auto
Replace the damaged gasket and
inspect cylinder head warp.
Repair seating surface if possible.
Adjust the valve clearance.
Replace the piston and/or cylinder
Inspect the cylinder and piston; repair or
replace them if necessary.
Replace the piston and/or the piston
Replace the auto-decompressor.