robo

im busy restoring a yzf750 1995. the cams were out when i bought it and had been placed in a box with other bits. iv put the camshafts back in but when i torque them up the cams will not turn. so im wondering if the head has warped [ i can not see any sign of it] iv also noticed 2 of the pistons have a slight crack in them ,, over heated may be ? the bike is a 4fm and the cam case is stamped with 3gm. could this be the reason why the cams will not turn and are to tight, wrong casing for 4fm cams? or are fz and yzf parts all interchangeable ? also i can get a good thunderace 1000 head and cams but will these fit a yzf 750 barrels ? any help would be very great full thank

hello. i am busy restoring a yzf750r 1995 and found a hair line crack in the skirts of two of the pistons. iv checked out the internet for a supplier that sells new pistons but not having much luck. anyone one no of a supplier? any help would great full. thanks