Popping through the carburetor in a combustion engine typically occurs due to a lean air-fuel mixture. A carburetor is responsible for mixing air and fuel in the correct proportion before delivering it to the engine for combustion. When the mixture is too lean, meaning there is not enough fuel in relation to the amount of air, it can lead to incomplete combustion.

The popping sound is usually a result of this incomplete combustion happening in the exhaust system. The unburned fuel-air mixture ignites in the hot exhaust manifold or the exhaust system, causing small explosions or popping noises.

Several factors can contribute to a lean air-fuel mixture, including:

1. Carburetor Settings: If the carburetor's fuel delivery is set too low, it can result in a lean mixture.
2. Air Leaks: Any unintended air leaks in the intake system, such as cracked hoses or gaskets, can cause an imbalance in the air-fuel mixture.
3. Fuel Delivery Issues: Problems with the fuel delivery system, such as a clogged fuel filter or a weak fuel pump, can lead to insufficient fuel reaching the carburetor.
4. Altitude and Temperature: Engine performance can be affected by changes in altitude and temperature, requiring adjustments to the carburetor settings to maintain the correct air-fuel ratio.
5. Modified Engines: Aftermarket modifications to the engine, like upgraded air intakes or exhaust systems, may require re-calibrating the carburetor for optimal performance.

To prevent popping through the carburetor, it's essential to ensure proper carburetor tuning and maintenance. Regularly inspecting the intake system for any leaks or damages and adjusting the carburetor settings according to the engine's needs can help maintain a balanced air-fuel mixture and smooth engine operation.