Patent ID: 8453629

Claim:
A spark-ignition engine comprising: a plug hole ( 13 ) provided with a plug-attaching aperture ( 12 ) at an innermost portion thereof and formed in a cylinder head ( 2 ); an ignition plug ( 10 ) engaged in screw-thread relationship with the plug-attaching aperture ( 12 ); and a plug, cap ( 9 ) integral with an ignition coil and attached to the ignition plug ( 10 ) upon insertion of the plug cap ( 9 ) into the plug hole ( 13 ), wherein the plug hole ( 13 ) is arranged at a position outside a head cover ( 5 ) at the cylinder head ( 2 ), a head surface ( 2 a ) being opened to provide the plug hole ( 13 ) and having a plug-cap attaching flange ( 11 ) attached thereto, the plug-cap attaching flange ( 11 ) being formed with an extending cylinder-portion ( 15 ) having an extension-hole ( 15 A) communicated with the plug hole ( 13 ), the plug cap ( 9 ), as inserted from the extension hole ( 15 A) into the plug hole ( 13 ), having a coil portion ( 9 C) fixed to the extending cylinder-portion ( 15 ), and wherein the plug-cap attaching flange ( 11 ) is attached to the head surface ( 2 a ) at a position spaced-apart from the head cover ( 5 ), the extending cylinder-portion ( 15 ) being spaced-apart from the head cover ( 5 ) and extending upwardly from the plug-cap attaching flange ( 11 ), the extension hole ( 15 A) of the extending cylinder-portion ( 15 ) being longer than the plug hole ( 13 ), and the coil portion ( 9 C) of the plug cap ( 9 ) being fixed to an upper end portion of the extending cylinder-portion ( 15 ) at a position spaced-apart from the head cover ( 5 ).