Hi Red : Bore is 44 mm or 1.73 in. Stroke is 36 mm or 1.42 in. Disp. 55 cc or 3.360cu. in.. And your right. Pretty well all of the older saws were magnesium. When I was converting a lot of engines, I used the trusty old hacksaw, as the stuff cuts like butter. Auto body file leaves a nice finish.
Have fun....Gord