1970-1973 Ski-Doo Snowmobiles Technical Data Manual, Page 33Get this manual
1972 MODEL
1NOMINAL DIMENSION OF CYLINDER BORE Engine 1st Oversize Standard Type inches mm inches mm 247 69.0 2.716 69.5 2.736 292 75.0 2.952 75.5 2.972 ,302 76.0 2.992 76.5 3.011 337 78.0 3.070 78.5 3.090 343 59.5 2.342 2.362 60.0 401 64.5 2.539 65.0 2.559 67.5 2.677 68.0 434 2.657 435 67.5 2.657 68.0 2.677 640 76.0 2.992 76.5 3.011 641 76.0 2.992 76.5 3.011 82.5 3.248 775 82.0 3.228 A 2nd Oversize at 77.0 mm (3.031") is also available
1973 MODEL
NOMINAL DIMENSION OF CYLINDER BORE
ENGINE TYPE 247 248 249 294 302 337 338 343 346 396 401 434 435 640 69.0 54.0 54.0 57.0 76.0 78.0 59.5 59.5 59.5 64.5 64.5 67.5 67.5 76.0