BSA 1949-58 M Models Parts Book

PISTON CHART-1949 to 1957 PISTON C01\1PLETE COl\llPRESSION RING SCRAPER RIN G Compresion Year l\'lodel Ratio Standard }mm. Irnm . Standa rd tmn1. Imm. Standard f rom. lmm . oversize oversize oversize oversize oversize oversize 1949 to 1953 M20 4.9 to 1 66-1190 69-1191 66-192 66-1090(2) 66-1091 (2) 66-1092(2) 66-1100 66-1101 66-1102 1954 66-109 1 ! 66-1095 66-1096 66-110 66-1101 66-1102 to 1VI20 4.9 to 1 66-1 93 66-1194 66--195 (top) (top) (top) 1957 66-124 66-12•15 66-1246 1949 to 1953 1\1121 5 to 1 66-1198 66-1199 66-1200 66-1090(2) 66-1091(2) 66-1092(2) 66-1100 66-1101 66-1102 1954 66-1094 66-1095 66-1096 66-100 66-1101 66-1102 to J\112 5 to 1 66-1215 66-1216 66-1217 (top) (top) (top) 1957 66-1244 66-1245 66-1246 1949 to 1952 NI33 6.8 to 1 65-1244 65-1260 65-1262 65--1250(2) 65-1251(2) 65-1252(2) 65-1253 65-1254 65-1255 1949 to 1952 1\•133 7.5 to 1 65-;-1264 65-1266 65-1268 65-1250(2) 65-1251(2)65-1252(2) 65-1253 65-1254 65-1255 1953 to 1955 ì\!133 6.5 to 1 65-1692 65-1694 65-1696 65-1250(2) 65-1251(2)65-1252(2) 65-1253 65-1254 65-1255 1953 to 1957 lVI33 7.5 to 1 65-1660 65-1662 65-1664 65-1250(2) 65-1251(2)65-1252(2) 65-1253 65-1254 65-1255 '1:954 to M21 1957 A.A. . 5 to 1 66-1198 66-1199 66-i200 66-1090(2)66-1091(2)66-1092(2) 66-1100 66-101 66-1102 !\: l.' ; ,;·. ~{ :·.:¡·::·:;: 1 "· 1953 to 1957 ì\1120 M21 M 33 . . 500c.c. S.V. 600c.c. S.V . 500c.c. O.H.V. · BivI20 Bìvl21 BM33 Bfvl20 Bl\'120 BM20 B1vl20S BlVI20S BM20S ENGINE and FRAME MARKINGS - 1949 to 1957 Year l:Vlodel Type Engine Frame (Rigid) Frame (Spring) 1951 to 1952 1949 to 1952 I\120 M21 M 33 500c.c. S.V. 600c.c. S.V. 50c.c. O.H.V. Zl\1120 ZM21 ZM33 ZM20 Zl\1120 ZM20 ZM 20S ZlVI20S Z1\120S ' 87