NOTE YOU MUST USE THE INCLUDED SPECIAL HEAD GASKET !! IF YOU HAVE ONE OF THE OLDER ALL ROUND HEAD GASKETS THEN YOU WILL NEED TO FILE DOWN SOME OF THE TIPS ON THE INCLUDED HEAD GASKET... (MAKE ALL POINTS EVEN LENGTH) 90BBK/53.50MM(S1415/335T) @ NEW TYPE VS OLD TYPE HEAD GASKET = KNOTCHED & ALL ROUND @ NEW TYPE (OR_OLD) OHV 90CC BIG BORE HEAD GASKET 1/21L (335T)FITS THE FOLLOWING ORIGINAL ENGINES: CT90'S K5, K6, AND 1976 TO 1979 ALL YEARS OF ST90'S ATC90'S WITH A ENGINE SERIAL NUMBER'S LARGER THAN 1113934 OR ABOUT 1972 AND NEWER 54.60MM ID 64.20MM OD .032" THE POINTED GASKET REPLACES THE NOTCHED ONE YES IF YOU NEEDED TO GET THE OLD TYPE HEAD GASKET JUST GRIND OFF THE POINTS AND BINGO !! 335T