Hi Mibato, that from Firecrackers when reducing, it can be that the mixture is very poor in gasoline and detone (see that the spark plug electrode is not whitish) and also if you carry the ignition out of the point of pointing to reducing when reducing. What I would do would be to clean the disassembled carburetor, changing the joints and adjusting the level of the float if necessary, the tarm may be dirty and from there that does not have the idle or by obstruction of the gum or by an air intake between the closing joint of the lid, also check the empty tubes that go to the actuators, they are not cracked or take air. Summarizing that it is best to check it when cleaning it well (these works should not be done halfway with a clean-carburers spray and already this ...)