The metal blade disc boss on the crank under the flywheel.
It is locked on to the flywheel via a taper.
Sit one side of the boss on an anvil and hit the other with a hammer and that should release the lock.
Then with the boss off you can wiggle the flywheel off. It is on a straight shaft, slides off but will be corroded etc, wiggle and lever and take care.
Then upturn the block on some bits of wood and drift the crank out. Do whatever you like to protect the thread. I use and old blade disc nut.
To pull it all back together you will need a big washer to replace the blade plate with and you can just use the big nut that holds the disk on. Might be a bit hard without a rattle gun.
Are the crank bearings stuffed?? Is the lower crank seal stuffed??? If the crank spins free and the seal is not leaking oil everywhere you are wasting your time pulling it apart. Just put the piston & rings in.
