Why is it spitting back through the carb not backfiring?

When an engine is "spitting back" through the carburetor, it typically indicates an issue with the air-fuel mixture or timing, causing combustion to occur in the intake tract instead of the combustion chamber. This phenomenon is often due to an overly rich mixture, incorrect ignition timing, or a malfunctioning carburetor. In contrast, backfiring refers to combustion occurring in the exhaust system, which can happen due to unburned fuel igniting late in the exhaust cycle. Thus, spitting back through the carb is a sign of intake-related issues, while backfiring pertains to problems in the exhaust system.