Abstract: A method and system for operating a two-stroke engine includes a fuel system comprising a fuel pressure sensor, fuel temperature sensor and a fuel injector and a controller in communication with the fuel pressure sensor and fuel temperature sensor. The controller controls the fuel injector with a fuel pulsewidth determined by determining a beginning time of a window for measuring fuel pressure, determining an ending time of the window, measuring fuel pressure between the beginning time and the ending time, determining a fuel pulsewidth based on the fuel pressure and fuel temperature and injecting fuel into the two-stroke engine in response to a desired fuel mass.

Abstract: An engine is disclosed having a water cooling system allowing efficient cooling of the exhaust valves to prevent temperature gradients from building in the engine. Water is therefore pumped through the engine though first and second water cooling cores which discharge through the head. A water manifold is positioned over the discharge opening and includes couplings for the radiator supply, radiator return, water pump supply, oil cooler supply and oil cooler return. The engine has separate chambers to isolate the pistons and cylinders, and reed valves cover the chambers and allow the blow-by gases and oil to enter the oil pan during the power stroke of the engine cycle.

Abstract: An engine is disclosed having a water cooling system allowing efficient cooling of the exhaust valves to prevent temperature gradients from building in the engine. Water is therefore pumped through the engine though first and second water cooling cores which discharge through the head. A water manifold is positioned over the discharge opening and includes couplings for the radiator supply, radiator return, water pump supply, oil cooler supply and oil cooler return. The engine has separate chambers to isolate the pistons and cylinders, and reed valves cover the chambers and allow the blow-by gases and oil to enter the oil pan during the power stroke of the engine cycle.

Abstract: An engine is disclosed having a water cooling system allowing efficient cooling of the exhaust valves to prevent temperature gradients from building in the engine. Water is therefore pumped through the engine though first and second water cooling cores which discharge through the head. A water manifold is positioned over the discharge opening and includes couplings for the radiator supply, radiator return, water pump supply, oil cooler supply and oil cooler return. The engine has separate chambers to isolate the pistons and cylinders, and reed valves cover the chambers and allow the blow-by gases and oil to enter the oil pan during the power stroke of the engine cycle.

Abstract: A two-wheeled vehicle includes a frame, a plurality of ground-engaging members for supporting the frame, and an engine supported by the frame and operably coupled to the ground-engaging members. Additionally, the two-wheel vehicle includes a down tube extending downwardly from a front end of the frame. A front fairing is supported on the down tube.

Abstract: An engine is disclosed having a water cooling system allowing efficient cooling of the exhaust valves to prevent temperature gradients from building in the engine. Water is therefore pumped through the engine though first and second water cooling cores which discharge through the head. A water manifold is positioned over the discharge opening and includes couplings for the radiator supply, radiator return, water pump supply, oil cooler supply and oil cooler return. The engine has separate chambers to isolate the pistons and cylinders, and reed valves cover the chambers and allow the blow-by gases and oil to enter the oil pan during the power stroke of the engine cycle.

Abstract: An engine is disclosed having a water cooling system allowing efficient cooling of the exhaust valves to prevent temperature gradients from building in the engine. Water is therefore pumped through the engine though first and second water cooling cores which discharge through the head. A water manifold is positioned over the discharge opening and includes couplings for the radiator supply, radiator return, water pump supply, oil cooler supply and oil cooler return. The engine has separate chambers to isolate the pistons and cylinders, and reed valves cover the chambers and allow the blow-by gases and oil to enter the oil pan during the power stroke of the engine cycle.

Abstract: An engine is disclosed having a water cooling system allowing efficient cooling of the exhaust valves to prevent temperature gradients from building in the engine. Water is therefore pumped through the engine though first and second water cooling cores which discharge through the head. A water manifold is positioned over the discharge opening and includes couplings for the radiator supply, radiator return, water pump supply, oil cooler supply and oil cooler return. The engine has separate chambers to isolate the pistons and cylinders, and reed valves cover the chambers and allow the blow-by gases and oil to enter the oil pan during the power stroke of the engine cycle.

Abstract: A vehicle includes a plurality of ground-engaging members and a frame supported by the ground-engaging members. The frame includes a front frame member and a rear frame member coupled to the front frame member. The vehicle also includes a powertrain assembly supported by the frame and an air intake assembly operably coupled to the powertrain assembly and the front frame member. The air intake assembly includes at least one air inlet member extending into a portion of the front frame member. The air inlet member extends from an inlet opening to an outlet opening, and a portion of the air inlet member intermediate the inlet and outlet openings has a diameter less than a diameter of the outlet opening.

Abstract: An engine is disclosed having a water cooling system allowing efficient cooling of the exhaust valves to prevent temperature gradients from building in the engine. Water is therefore pumped through the engine though first and second water cooling cores which discharge through the head. A water manifold is positioned over the discharge opening and includes couplings for the radiator supply, radiator return, water pump supply, oil cooler supply and oil cooler return. The engine has separate chambers to isolate the pistons and cylinders, and reed valves cover the chambers and allow the blow-by gases and oil to enter the oil pan during the power stroke of the engine cycle.

Abstract: An engine is disclosed having a water cooling system allowing efficient cooling of the exhaust valves to prevent temperature gradients from building in the engine. Water is therefore pumped through the engine though first and second water cooling cores which discharge through the head. A water manifold is positioned over the discharge opening and includes couplings for the radiator supply, radiator return, water pump supply, oil cooler supply and oil cooler return. The engine has separate chambers to isolate the pistons and cylinders, and reed valves cover the chambers and allow the blow-by gases and oil to enter the oil pan during the power stroke of the engine cycle.

Abstract: An engine is disclosed having a water cooling system allowing efficient cooling of the exhaust valves to prevent temperature gradients from building in the engine. Water is therefore pumped through the engine though first and second water cooling cores which discharge through the head. A water manifold is positioned over the discharge opening and includes couplings for the radiator supply, radiator return, water pump supply, oil cooler supply and oil cooler return. The engine has separate chambers to isolate the pistons and cylinders, and reed valves cover the chambers and allow the blow-by gases and oil to enter the oil pan during the power stroke of the engine cycle.

Abstract: An engine is disclosed of the V-configuration having an integrated engine and transmission. The engine has an engine ventilation system communicating between the crankcase and an upper end of the valve cover, whereby blow-by gases can be returned to the air intake system to recycle the unspent fuel. The engine also includes an easily accessible/removable cam, such that the camshaft may be removed without removing the rocker arms. The engine also includes a lubrication system for lubricating components of the engine and transmission.

Abstract: An internal combustion engine includes a crankcase including a crankshaft and at least one cylinder coupled to the crankcase. The at least one cylinder has an intake port and defines an internal combustion chamber. The engine further includes a throttle body assembly with a throttle valve coupled to the intake port of the at least one cylinder and a throttle plate. Additionally, the engine includes a supplementary air inlet fluidly coupled to the intake port and spaced apart from the throttle valve. The supplementary air inlet is configured to receive a flow of air from a location downstream of the throttle plate when the throttle plate is in a fully closed position and the flow of air is directed into the combustion chamber through the intake port for combustion therein.

Abstract: An engine includes a first cylinder communicating with a first intake port and a first exhaust port, and an exhaust assembly coupled to the engine and including a first exhaust manifold coupled to the first exhaust port. The first exhaust manifold is angled relative to the first exhaust port.

Abstract: An engine is disclosed having a water cooling system allowing efficient cooling of the exhaust valves to prevent temperature gradients from building in the engine. Water is therefore pumped through the engine though first and second water cooling cores which discharge through the head. A water manifold is positioned over the discharge opening and includes couplings for the radiator supply, radiator return, water pump supply, oil cooler supply and oil cooler return. The engine has separate chambers to isolate the pistons and cylinders, and reed valves cover the chambers and allow the blow-by gases and oil to enter the oil pan during the power stroke of the engine cycle.

Abstract: An engine is disclosed having a water cooling system allowing efficient cooling of the exhaust valves to prevent temperature gradients from building in the engine. Water is therefore pumped through the engine though first and second water cooling cores which discharge through the head. A water manifold is positioned over the discharge opening and includes couplings for the radiator supply, radiator return, water pump supply, oil cooler supply and oil cooler return. The engine has separate chambers to isolate the pistons and cylinders, and reed valves cover the chambers and allow the blow-by gases and oil to enter the oil pan during the power stroke of the engine cycle.

Abstract: An engine includes a first cylinder communicating with a first intake port and a first exhaust port, and an exhaust assembly coupled to the engine and including a first exhaust manifold coupled to the first exhaust port. The first exhaust manifold is angled relative to the first exhaust port.

Abstract: A two-wheeled vehicle includes a frame having a front frame portion, a mid-frame portion, and a rear frame portion. The mid-frame portion is coupled to the rear frame portion and the front frame portion. The vehicle further includes a plurality of ground-engaging members for supporting the frame. The front frame portion is removably coupled to the mid-frame portion with a plurality of frame members extending between the front frame portion and the mid-frame portion.

Abstract: An internal combustion engine includes a crankcase including a crankshaft and at least one cylinder coupled to the crankcase. The at least one cylinder has an intake port and defines an internal combustion chamber. The engine further includes a throttle body assembly with a throttle valve coupled to the intake port of the at least one cylinder and a throttle plate. Additionally, the engine includes a supplementary air inlet fluidly coupled to the intake port and spaced apart from the throttle valve. The supplementary air inlet is configured to receive a flow of air from a location downstream of the throttle plate when the throttle plate is in a fully closed position and the flow of air is directed into the combustion chamber through the intake port for combustion therein.