Abstract: A fuel enrichment device includes a body forming a first fuel chamber and a second fuel chamber. The second fuel chamber is adapted to contain a predetermined amount of enriching fuel to be provided to an engine. A normally open valve connects the first fuel chamber to the second fuel chamber. A normally closed valve for controls the provision of enriching fuel to the engine. The normally closed valve is open whenever the normally open valve is closed.

Abstract: A bar adjustment assembly for a chain saw includes a shaft, a bar adjustment pin that is journalled for rotation relative to the shaft, and a pin alignment spring that biases the pin toward an engagement position. A void is provided for accommodating the pin as it is rotated away from the engagement position by a guide bar that has been incorrectly attached.

Abstract: A fuel enrichment device includes a body forming a first fuel chamber and a second fuel chamber. The second fuel chamber is adapted to contain a predetermined amount of enriching fuel to be provided to an engine. A normally open valve connects the first fuel chamber to the second fuel chamber. A normally closed valve for controls the provision of enriching fuel to the engine. The normally closed valve is open whenever the normally open valve is closed.

Abstract: A device for a power tool that includes an internal combustion engine and a carburetor for supplying an air and fuel mixture to the engine. The carburetor includes at least one externally adjustable component. An air filter arrangement of the device is for in-taking air, filtering the air, and directing the filtered air to the carburetor. The arrangement includes a housing. A tamper-resisting portion of the device extends from the air filter arrangement housing and extends adjacent to the location of the at least one adjustable component. The tamper resisting portion includes a segment that permits access to the at least one adjustable component along a first direction and limits access to the at least one adjustable component off of the first direction.

Abstract: The cooperative operational relationship among an ignition switch, choke mechanism and air filter unit for a portable power tool are integrated in a way to improve that relationship. The ignition switch and choke mechanism are arranged in a coactive relationship wherein the ignition switch and a choke lever in the choke mechanism have engaging parts such that the ignition switch is moved to an “On” position by the choke lever when the choke lever is moved to a position where it has reduced the air flow to a carburetor. A spring engaging the ignition switch is biased for applying a force to the ignition switch in a direction toward a mounting element on which the ignition switch is mounted and away from the choke lever. In a particular embodiment, the ignition switch is mounted on the air filter unit.

Abstract: The cooperative operational relationship among an ignition switch, choke mechanism and air filter unit for a portable power tool are integrated in a way to improve that relationship. The ignition switch and choke mechanism are arranged in a coactive relationship wherein the ignition switch and a choke lever in the choke mechanism have engaging parts such that the ignition switch is moved to an “On” position by the choke lever when the choke lever is moved to a position where it has reduced the air flow to a carburetor. A spring engaging the ignition switch is biased for applying a force to the ignition switch in a direction toward a mounting element on which the ignition switch is mounted and away from the choke lever. In a particular embodiment, the ignition switch is mounted on the air filter unit.

Abstract: A piston channel is provided for a piston of an air scavenging internal combustion engine. The channel extends radially inward partially around a circumference of a piston body. An edge wall of the channel is sloped towards a wrist pin aperture in the piston to improve purging efficiency of a transfer duct.

Abstract: A tamper resistant mixture adjustment screw arrangement for a carburetor. The arrangement includes a carburetor body having at least one air/fuel adjustment screw threaded therein. The adjustment screw has a threaded shank and a head portion. The head portion is defined by a smooth top surface and an undulant, uneven side surface capable of being engaged and mated by an adjusting tool having a complementary undulant, uneven side surface capable of being engaged and mated by an adjusting tool having a complementary undulant, uneven surface for initially adjusting the air/fuel mixture in the carburetor. A blocking curb extends from the carburetor body to a level which at least substantially corresponds to a projecting extent of each adjustment screw and being closely spaced to the screw head to prevent the screw from being turned by commonly available tools, but to permit the screw to be adjusted by the adjusting tool.

Abstract: A tamper resistant mixture adjustment screw arrangement for a carburetor. The arrangement includes a carburetor body having at least one air/fuel adjustment screw threaded therein. The adjustment screw has a threaded shank and a head portion. The head portion is defined by a smooth top surface and an undulant, uneven side surface capable of being engaged and mated by an adjusting tool having a complementary undulant, uneven side surface capable of being engaged and mated by an adjusting tool having a complementary undulant, uneven surface for initially adjusting the air/fuel mixture in the carburetor. A blocking curb extends from the carburetor body to a level which at least substantially corresponds to a projecting extent of each adjustment screw and being closely spaced to the screw head to prevent the screw from being turned by commonly available tools, but to permit the screw to be adjusted by the adjusting tool.

Abstract: A carbureted two-cycle engine including an intake channel, a choke valve in the intake channel fixed to a pivotable choke valve shaft and lever, and a throttle valve in the intake channel fixed to a pivotable throttle valve shaft and lever. The engine includes an air channel in communication with fresh air, and an air valve fixed to a pivotable air valve shaft and lever. A piston within a cylinder of the engine includes a transfer port for intermittently connecting the intake channel and the air channel with a combustion chamber. An activating lever pivotably mounted to the air valve shaft transmits movement of the throttle lever to the air valve lever after a predetermined angle of rotation of the throttle lever. A fast idle latch is engagable by the choke lever to hold the throttle lever in a fast idle position until the throttle lever is separately moved.

Abstract: A carbureted two-cycle engine including an intake channel, a choke valve in the intake channel fixed to a pivotable choke valve shaft and lever, and a throttle valve in the intake channel fixed to a pivotable throttle valve shaft and lever. The engine includes an air channel in communication with fresh air, and an air valve fixed to a pivotable air valve shaft and lever. A piston within a cylinder of the engine includes a transfer port for intermittently connecting the intake channel and the air channel with a combustion chamber. An activating lever pivotably mounted to the air valve shaft transmits movement of the throttle lever to the air valve lever after a predetermined angle of rotation of the throttle lever. A fast idle latch is engagable by the choke lever to hold the throttle lever in a fast idle position until the throttle lever is separately moved.

Abstract: A tamper resistant mixture adjustment screw arrangement for a carburetor. The arrangement includes a carburetor body having at least one air/fuel adjustment screw threaded therein. The adjustment screw has a threaded shank and a head portion. The head portion is defined by a smooth top surface and an undulant, uneven side surface capable of being engaged and mated by an adjusting tool having a complementary undulant, uneven side surface capable of being engaged and mated by an adjusting tool having a complementary undulant, uneven surface for initially adjusting the air/fuel mixture in the carburetor. A blocking curb extends from the carburetor body to a level which at least substantially corresponds to a projecting extent of each adjustment screw and being closely spaced to the screw head to prevent the screw from being turned by commonly available tools, but to permit the screw to be adjusted by the adjusting tool.