Stiff turn-over of new engine, possible causes

Right, for starters, you havn't done what I did and greased the BACKs of the shells as well as the fronts?

If you loosen the main caps and big ends and the thing is still stiff it may be the thrusts. Some are made with plating on both sides these days. You need to either sand the backs a bit or fit a worn thrust on the cyl #2 side. I had to do this.

Are the bearings standard size? It's a case of tighten each bearing one by one until you find out which is causing the stiffness. You should be looking at ~15lbft max torque to rotate the assembled crank and pistons.