Can you move the flywheel freely through the first part of the stroke? i.e. put the piston at BDC and you should easily be able to move it up and down between where the pinch starts and BDC. If so, you are fine and that is normal. My RB V12 had such a tight pinch through the first gallon that I had to keep a screwdriver around to unstick the piston from TDC when starting (I had to pry the flyweel with a screwdriver to unstick the piston). It took several hours to get it to start the first time. Some engines just have too much pinch to start with, but those engines usually last the longest as well.