[KTL]

Make sure you have the nuts inside the oil cooler recess removed. The case has alignment sleeves for the rear main bearing (#1) in this location and they are typically the buggers that keep you from getting the case apart easily. Also there's a lone nut inside the chain port on the left (cyls 1-2-3) side of the case.

Otherwise yes it's often a patience exercise of tapping to get the halves to separate. Often helps to use VERY light pressure/leverage from a spreader type of tool to help coax the case apart. A good place to do this is where there is a lot of meat in the case area, like on the top where the breather cover goes. Can also do it at the area near the fan housing support area. Again, don't go crazy with the leverage. Any tool you use should be a light finger twisting amount of effort. Any more than that and you're risking breakage. Do NOT leverage it anywhere that is a critical sealing area or a fragile/unsupported area by surrounding case material.