An engine system may include a fuel and air supply circuit and an exhaust circuit, a temperature sensor mounted on an exterior of the engine and an oxygen sensor located in the exhaust circuit. The fuel and air supply circuit may include a throttle body mounted on the engine and having a throttle valve to control the flow rate of air delivered to the engine, a fuel injector carried by the throttle body to deliver fuel to the engine and a fuel rail carried by at least one of the throttle body and the fuel injector and having an input to receive a supply of fuel and an outlet through which fuel is routed to the fuel injector. An engine control unit may be communicated with these components to control the fuel and air mixture provided to the engine as a function of the temperature and oxygen sensor outputs.