Abstract: An internal combustion engine includes pressure relief devices that reduce pressure due to compression during startup, thereby decreasing the force needed to start the engine. A pressure relief valve mounts on top of the cylinder head and includes a duct to the combustion chamber leading to the valve and a second duct leading to the exhaust port so that gases in the combustion chamber may be vented through the exhaust system. A mechanical actuator having cables directed to each of the pressure relief valves for each of the cylinders manually actuates a first embodiment. A second embodiment includes a solenoid with wiring tied into a starter circuit that actuates the multiple valves from a single actuator.

Abstract: A sensing system for measuring the angular displacement of a rotating shaft is disclosed. The sensing system comprises a rotor and a sensor assembly disposed within the rotor. The rotor is constructed and arranged to be securably mounted to the shaft such that the rotor rotates in concert with the shaft. Furthermore, the rotor defines a plurality of teeth extending radially inwardly towards a center of the shaft. The sensor assembly comprises a sensor housing and a magnet arrangement disposed within the housing. The magnet arrangement defines a magnetic flux path between the sensor assembly and the rotor. As a result, the magnet arrangement and the rotor cooperate to define a magnetic circuit. Changes in magnetic flux through the magnetic circuit can be measured to determine the angular displacement of the rotating shaft.

Abstract: A method of modifying the cam drive arrangement of a motorcycle engine. The method includes providing an existing cam gear arrangement having a crankshaft sprocket connected to a primary camshaft sprocket with a chain, removing the chain, replacing each of the sprockets with a crankshaft gear and primary camshaft gear respectively, and engaging teeth of the gears so the crankshaft gear drives the primary camshaft gear directly. A specific method for modifying a TWIN CAM 88 engine, made by Harley-Davidson, according to this method, is also described.

Abstract: A breather valve and arrangement for an internal combustion engine, having a scavenge hole that is open for a relatively long period of time relative to piston travel. Scavenge hole preferably subtends an angle of between 20° and 150°, and preferably is open from between 30° and 135° of piston travel. A method of replacing an existing breather valve with this novel breather valve is also described. Other arrangements for achieving the advantages of the novel breather valve are also described.

Abstract: The present invention provides an internal combustion engine component, such as a cylinder head or tappet block, which is adaptable to a variety of pushrod positions and angles. A large pushrod aperture is formed in the engine component. The aperture is large enough to accommodate one or more pushrods passing therethrough at a variety of different angles and positions. A composite pushrod hole adapter plate is attached to the engine component over the aperture. The adapter plate has one or more pushrod holes machined therethrough at desired angles and positions. A counter bore is preferably formed around each pushrod hole to provide a seat for the end of a pushrod housing. A plurality of different adapter plates, having pushrod holes and counter bores formed therein at different angles and positions, may alternatively be attached to the engine component, thereby adapting the engine component for use in combination with various different engine designs.

Abstract: An evaporative emissions control system for carburetors used in the internal combustion engines of vehicles, such as motorcycles, has an evaporative emissions control valve attached to the carburetor in the air intake path to the carburetor. The evaporative emissions control valve may be implemented as a sub-assembly add-on or as an integral part of a carburetor or back plate. The evaporative emissions control valve includes a valve, such as a rotatable plate valve, which may be electrically operated by an electrical actuator, such as a dual-wound solenoid actuator. At engine start-up, when the vehicle ignition switch and starter switch are both closed, both windings of the solenoid actuator are energized to provide a strong opening force for the evaporative emission control valve. During steady-state running of the engine, only a single solenoid winding is energized by the power provided through the ignition switch, to maintain the evaporative emissions control valve in the open position.

Abstract: A lightweight pushrod assembly for internal combustion engines, such as motorcycle racing engines, includes a top pushrod and a bottom pushrod which are joined by a pushrod tappet. The pushrod tappet is mounted for reciprocating movement in a pushrod stanchion, and the stanchion is secured to the engine such that support is provided to the pushrod assembly at a position near the middle of the entire pushrod assembly. The pushrod stanchion also provides part of a pushrod housing assembly, with additional upper and lower housings provided to enclose the upper and lower pushrods. The lower end of the top pushrod and the upper end of the bottom pushrod preferably engage the tappet in a ball and socket joint relation to allow limited radial movement of the top and/or bottom pushrods to minimize the stresses on the pushrods. The supported pushrod assembly may be provided in kits for installation of the pushrod assemblies on existing engines.

Abstract: An internal combustion engine has a cylinder head with a combustion chamber defined by a depression in the head. The raised face surface of a piston extends into the combustion chamber in the cylinder head as the piston approaches top dead center, and creates turbulent squish currents within the chamber as closely matching surfaces on the piston face and on the walls of the combustion chamber in the head force gases out from between these surfaces. The turbulence helps to prevent autoignition and allows higher compression ratios than would otherwise be possible.

Abstract: A valve spring top collar is formed by a unitary body having a circular top face and a bottom surface, with a first circular shoulder extending downwardly from the bottom surface of the body and a second inwardly spaced circular shoulder. The shoulders are inserted into the valve springs so that the springs cannot slip off the collar in a radial direction. A central aperture extends through the central core of the body, through which a valve stem is inserted. A plurality of peripheral apertures extend through the body about the central aperture, thereby decreasing the total weight of the collar and allowing flow of lubricant to the springs.

Abstract: A butterfly type motorcycle carburetor including a housing having an induction passage and a venturi intermediate the ends of the passage, a butterfly valve assembly positioned in the induction passage downstream from the venturi and a fuel bowl mounted on the housing and forming a fuel reservoir below the induction passage. A main discharge tube is mounted in the housing with one end extending into the venturi in the induction passage and the other end into the fuel reservoir in the fuel bowl. An accelerator pump system is provided in the carburetor which includes a discharge nozzle that extends into the induction passage downstream from the venturi for directing fuel discharged from the nozzle toward the butterfly valve. An enrichment system is provided in the carburetor which can be selectively set at any position. A low speed air/fuel metering system is provided in the housing for low speed operation.