[Capo]

A cotter bolt has a tapered flat machined on it, the act of tightening the nut draws the taper onto the shaft thus securing it.
You need to give them a good clout with a hammer and a punch as you have to free the taper locking action. Don't worry too much about damaging the end of the bolt as they are cheap to replace.
Do not try to turn the bolt as the interface between the taper and shaft prevents rotation.

Once you have removed both cotters, the shaft can be driven out. However it is not unknown for the products of corrosion to seize them together, you best get a sturdy drift made up with a pilot so you can get some good wacks on it. Keep in mind that there are needle bearings and oil seals in the engine casing, damage them and you probably (given your financial situation) won't be riding it for a while.

Or you could take it to Rosso Corse I'm sure Ray would have it out in a jiffy.