Not revving up the engine when starting a motorcycle typically does not have any significant consequences. Modern motorcycles are equipped with automatic idle controls and fuel injection systems that regulate the engine's idle speed.
Choke: If your motorcycle has a manual choke, revving the engine while engaging the choke can assist in maintaining a stable idle until the engine warms up.
Carbureted Motorcycles: Older motorcycles with carburetors may require a slight rev during startup to ensure a smooth idle. This helps to prevent stalling or rough running until the engine reaches its operating temperature.
It's worth noting that excessive or aggressive revving of the engine, whether during startup or while riding, can lead to unnecessary wear and tear on the engine components and may be considered poor riding etiquette in some situations.
In general, following the manufacturer's recommendations for starting and warming up your motorcycle is the best practice. Consult your motorcycle's owner manual for specific instructions on how to start and operate your particular model.