Motorcycles typically have a separate carburetor for each cylinder for a few reasons:
Individual cylinder tuning: Each cylinder of a motorcycle engine has its own combustion characteristics and requirements due to variations in air/fuel mixture needs, exhaust flow, and other factors. Having separate carburetors allows for more precise tuning of each cylinder's fuel delivery, optimizing performance and ensuring balanced power across all cylinders.
Space limitations: Motorcycles have more space constraints compared to cars, especially sport bikes and other compact models. Using separate carburetors for each cylinder allows for a more efficient use of available space within the motorcycle's frame.
Enhanced throttle response: Individual carburetors provide more direct control over the air and fuel mixture for each cylinder. This can result in improved throttle response, as changes in throttle position are immediately reflected in the corresponding carburetor's operation.
Simplicity of design and maintenance: Carburetors are generally simpler in design compared to fuel injection systems, and having separate carburetors for each cylinder simplifies the overall design and maintenance of the fuel delivery system. It can be easier to troubleshoot and fine-tune individual carburetors rather than dealing with a complex central system.
That said, it's worth noting that modern motorcycles have shifted towards fuel injection systems, which offer better fuel efficiency, precise control, and improved emissions. Fuel injection systems can provide individual cylinder fuel control as well, but they achieve it through electronic sensors and injectors rather than separate physical components like carburetors.