High-Compression Engine - Honda GX690 Workshop Manual

TECHNICAL FEATURES

HIGH-COMPRESSION ENGINE

TECHNICAL FEATURES
OUTLINE
The GX630/GX630R/GX660/GX660R/GX690/GX690R engines have more combustion efficiency and cylinder cooling capability
than previous models. This results in increased the compression (increased to 9.3 from 8.3) and higher engine output.
FEATURE
Combustion efficiency and intake/exhaust efficiency improvement
Combustion efficiency improvement: The S/V ratio (Surface Volume ratio of the combustion chamber) and resulting thermal
efficiency have been increased by making the combustion chamber hemispherical.
The offset distance of the spark plug position has been decreased and the equality of the flame propagation has been increased by
moving the spark plug closer to the center of the combustion chamber.
Intake/exhaust efficiency improvement: Arranging the valves in a radial pattern allows the cylinder to have smoother intake and
exhaust ports, and the port angle has been narrowed.
NEW GX630/GX630R/GX660/GX660R/GX690/GX690R:
Cooling efficiency improvement
The cylinder block has been integrated with the cylinder head. It eliminates the use of the low thermal conductivity steel cylinder
head bolts and stainless-steel cylinder head gaskets. Tubes are placed on the outside of the cylinder for push rod passages,
allowing the cylinder block to be thinner and increase cooling efficiency.
NEW GX630/GX630R/GX660/GX660R/GX690/GX690R:
CYLINDER
INTEGRATED WITH
CYLINDER HEAD
16-2
PUSH ROD PASSAGE
PIPE
CRANKCASE
PREVIOUS MODEL:
PREVIOUS MODEL:
CYLINDER HEAD
BOLT
PUSH ROD PASSAGE
CYLINDER
HEAD
CYLINDER HEAD
GASKET
CYLINDER
BARREL