A carburetor with rotary valve includes an idle adjustment needle with an eccentric hole, accordingly a special adjustment tool used for idle adjustment needle has an eccentric boss; a carburetor with rotary valve includes an idle adjustment needle with an eccentric boss, accordingly a special adjustment tool used for idle adjustment needle has an eccentric hole. The idle adjustment needle must be cooperated with the special adjustment tool to carry out the adjustment, thus non-professional user can not casually adjust the fuel oil needle without the special tool, so that the engine can be maintained in the best setting condition to ensure the engine exhaust to meet the environmental protection requirement.