Have you checked that the conrod is straight and that the small end was reamed in line? or was the small end not touched? It might be a good idea to remove the piston from the conrod and to try pushing the piston up the barrel to see if there is still resistance when you try that. Were the crankcase bearings line reamed correctly? Or have you not touched the bearing housings? Are the piston rings orientated correctly and not spreading when you reach the ports and catching? Lots of things could cause your problems.
