I use a slide hammer to remove the rocker shafts. You need a 6mm 1pitch bolt and it can be a very tight fit into the hole.
After removing the sheet metal parts I rotate the cam until the pin is in the 12 o'clock position and then slide hammer the cam and aluminum bearing out. The pin must be in the 12 o'clock position.
There are two cut outs for the lobes in the head. If the camshaft isn't aligned it won't come out or you will do damage.
You might have to heat the head up in case someone glued the rocker shafts in with Red LocTite.
Slide hammer in action.
Good luck! Tony