Put the stem in a vice and turn the fork. Or, put an old wheel in the fork, one you dont mind bending a bit, and that will give you more leverage.
Or, find some coduit that will fit up the steerer, if you have a front brake fitted you will need to remove it, put the fork in a vice, shove the conduit up the steerer so it is in contact with bottom of stem, hit with hammer.
OR put the headtube in a vice, front wheel between your knees, a bit of conduit up your arse, tuck your bits between your thighs, squirt 3-in-1 over your chest and hit it with a mallet.
Put the stem in a vice and turn the fork. Or, put an old wheel in the fork, one you dont mind bending a bit, and that will give you more leverage.
Or, find some coduit that will fit up the steerer, if you have a front brake fitted you will need to remove it, put the fork in a vice, shove the conduit up the steerer so it is in contact with bottom of stem, hit with hammer.
OR put the headtube in a vice, front wheel between your knees, a bit of conduit up your arse, tuck your bits between your thighs, squirt 3-in-1 over your chest and hit it with a mallet.