PURPOSE: To improve air-tightness while preventing deformation of the body of a carburetor, by holding the carburetor body between an insulator and an air-cleaner through a sleeve and an elastic sealing member longer than the carburetor.

CONSTITUTION: A carburetor body 7 is secured through bolts 13 between an insulator 1 having an air supply hole 2 and an air-cleaner 3 through a sleeve 8 slightly longer than the carburetor body 7. First and second sealing members 11, 12 composed of elastic material are arranged respectively between the carburetor body 7 and the insulator 1 and between the carburetor body 7 and the air-cleaner 3. Consequently, air-tightness of carburetor is improved and the carburetor body can be prevented from deformation.