A vehicle, such as a motorcycle, which has an engine control system that is configured to reduce an output of the engine upon a determination that a shifting of the transmission, without a corresponding disengagement of the clutch, is likely to occur. In one arrangement, the vehicle includes a controller that is configured such that if a release rate of the accelerator, calculated on the basis of signals from an accelerator position sensor, has been equal to or larger than a threshold value for a period of time, and other conditions have been met, it is determined that snapping of the accelerator by the operator has been performed. The snapping is a release of the accelerator that is predicted to be accompanied by a transmission shift without disengagement of the clutch. In response to the snapping determination, the engine output is reduced for a reduction duration, such as by retarding the ignition timing, after the elapse of a predetermined stand-by time.