A control system of carburation of a two-stroke internal combustion engine comprising following activities: a. operating the engine with an air/fuel ratio of a predetermined initial value (λ 0): b. for the initial value (λ 0) of the air/fuel ratio, constructing a first curve (c i (α)) representing the ionization current (c i) as a function of the angular position (α) of a crankshaft of the engine, the ionization current (c i) being measured through spark plug electrodes; c. calculating a value (z 0) equal to an integral of the first curve (c i (α)) in a predetermined angular interval of the crankshaft; d. interrupting fuel supply for a few engine cycles, thereby increasing the air/fuel ratio of the engine to a second value (λ 1)) larger than the initial value (λ 0), the second value (λ 1) of the air/fuel ratio being equal to the sum of the initial value (λ 0) and a predetermined quantity (Δ λ), the predetermined quantity (Δ λ) being smaller than or equal to 0.05; b. for the second value (λ 1) of the air/fuel ratio, constructing a second curve (c i (α)) representing the ionization current (c i) as a function of the angular position (α) of the crankshaft, the ionization current (c i) being measured through the spark plug electrodes; c. calculating a value (z 1) equal to an integral of the second curve (c i (α)) in a predetermined angular interval of the crankshaft that is equal to the preceding angular interval; g. calculating a difference (Δ z) as the value (z 1) of the integral of the second curve minus the value (z 0) of the integral of the first curve; h. if the difference (Δz) has an absolute value greater than a predetermined threshold value (Δ zrif), intervening on the carburation to regulate the quantity of fuel injected, wherein the regulating of the quantity of fuel injected includes increasing the quantity of fuel injected in a case of a negative difference and reducing the quantity of fuel injected in a case of a positive difference. a. operating the engine with an air/fuel ratio of a predetermined initial value (λ 0): b. for the initial value (λ 0) of the air/fuel ratio, constructing a first curve (c i (α)) representing the ionization current (c i) as a function of the angular position (α) of a crankshaft of the engine, the ionization current (c i) being measured through spark plug electrodes; c. calculating a value (z 0) equal to an integral of the first curve (c i (α)) in a predetermined angular interval of the crankshaft; d. interrupting fuel supply for a few engine cycles, thereby increasing the air/fuel ratio of the engine to a second value (λ 1)) larger than the initial value (λ 0), the second value (λ 1) of the air/fuel ratio being equal to the sum of the initial value (λ 0) and a predetermined quantity (Δ λ), the predetermined quantity (Δ λ) being smaller than or equal to 0.05; b. for the second value (λ 1) of the air/fuel ratio, constructing a second curve (c i (α)) representing the ionization current (c i) as a function of the angular position (α) of the crankshaft, the ionization current (c i) being measured through the spark plug electrodes; c. calculating a value (z 1) equal to an integral of the second curve (c i (α)) in a predetermined angular interval of the crankshaft that is equal to the preceding angular interval; g. calculating a difference (Δ z) as the value (z 1) of the integral of the second curve minus the value (z 0) of the integral of the first curve; h. if the difference (Δz) has an absolute value greater than a predetermined threshold value (Δ zrif), intervening on the carburation to regulate the quantity of fuel injected, wherein the regulating of the quantity of fuel injected includes increasing the quantity of fuel injected in a case of a negative difference and reducing the quantity of fuel injected in a case of a positive difference.