Remove the carburetor, cylinder head, and rear cover. After you remove the cylinder head and rear cover, slide the cylinder liner straight up out of the case. This will give you enough room to slide the con-rod off the crank pin. Make sure you note which side is facing towards the back, you have to reinstall it the same way.

Now you can slide the crank out the back of the engine, and you have a bare crankcase with only the bearings in it. Heat the case to about 250 degrees F, and the bearings should fall out when you rap the case against a block of wood. Clean the case, heat it again, and then slide in the new bearings...they should NOT be heated. Use the crankshaft to help with alignment. If you must tap the bearings, only tap them on the outer edge. Do not tap them in the center or on the balls.

Reassemble the engine in the reverse order you took it apart.