Abstract: A failure detection system for an air-to-fuel ratio control system includes a exhaust gas monitor positioned upstream of a catalytic converter for monitoring an emission content of exhaust gas based on which an air-to-fuel ratio is feedback controlled so as to be maintained at a desired ratio. The system has another exhaust gas monitor positioned downstream of the catalytic converter for monitoring an emission content of exhaust gas passed through the catalytic converter. Functional failures of the exhaust gas monitor of the air-to-fuel ratio control system is judged to be present on the basis of detected emission contents only when a predetermined threshold amount of intake air is detected.

Abstract: A failure detection system for an air-to-fuel ratio control system includes a exhaust gas monitor positioned upstream of a catalytic converter for monitoring an emission content of exhaust gas based on which an air-to-fuel ratio is feedback controlled so as to be maintained at a desired ratio. The system has another exhaust gas monitor positioned downstream of the catalytic converter for monitoring an emission content of exhaust gas passed through the catalytic converter. Functional failures of the exhaust gas monitor of the air-to-fuel ratio control system is judged to be present on the basis of detected emission contents only when a predetermined threshold amount of intake air is detected.

Abstract: Improved apparatus for supplying lubricating oil to the chain of a chain saw powered by an internal combustion engine. A lubricating oil tank is pressurized by communication with the crankcase of the engine, and the pressure forces oil from the oil tank to lubricate the saw chain. An air control valve is disposed in the air passage between the crankcase and the lubricating oil tank, and this valve is selectively operable to adjust the pressurization of the oil tank. The control valve is manually adjustable to adjust the pressurization of the lubricating oil tank, so as to accommodate changes in lubrication caused by factors such as changes in temperature, lubricating oil viscocity, or the like.

Abstract: A vibration-damping device is disclosed for damping the vibrations between a vibration generating and a vibration receiving assembly such as is found with the casing and the handles of a chain saw. In a preferred embodiment, the chain saw casing is provided with a fitting hole having two pairs of radially projecting arcuate portions each designed for abutting engagement with radially projecting fitting members. The first fitting members are provided at the circumference of a cylinder of elastic material which is attached for the vibration receiving assembly. The second radially projecting fitting members are provided at the circumference of a head piece which mounts on the casing and holds the elastic cylinder in place.