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The combustion chambers are modified by cutting work but the edges shown must be
hand finished for smooth corners.
NOTE
When grinding the cylinder head surface or using thinner gasket, adjust the valve timing
to keep that the valve to piston clearance is not less than the minimum value (IN: 0.7 mm,
EX: 1.2 mm).
Cylinder Compression
To adjust the cylinder compression, adjust the thickness of the cylinder head gasket or
smooth the cylinder head under surface or cylinder top surface to make the piston squish
0.65 mm. Keep the piston squish more than 0.65 mm.
Grind off the cylinder head under surface to 0.4 mm. Do not grind the cylinder upper
surface. This can raise the compression ratio while keeping the clearance of the piston
and valve, and one of the squish. Although, as the engine machining is uneven,
determine the cutting dimension after keeping the recess and the squish before
machining.
Position the piston at Top Dead Center, and put a small piece of modeling clay on the
shoulder of the piston. Install the cylinder head gasket and cylinder head, and tighten the
head bolts to the specified torque.
Remove the cylinder head and measure the thickness of the clay. The thickness of the
collapsed clay is the size of the squish.
The most preferable squish measurement is 0.65 mm.
Select proper cylinder head gasket.
Cylinder Head Gasket
Part No. Tightening thickness Remarks
11004-0026
0.65 mm STD
KIT
11004-0052 0.60 mm KIT
11004-0022 0.55 mm KIT
11004-0034 0.50 mm KIT
11004-0023 0.45 mm KIT
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