Who did the rebuild, and what was done? Was the the rod bearings changed, was the rod or rods "mic-ed", were assembly lubed used? Are the piston walls lubed? Were the bolts torque to specs. If you changed the battery and the starter motor than you have high engine resistance. Try squirting some oil in each cylinder, with all spark plugs off, use ratchet and rotate to get some oil on walls. Rotation should be very easy with no pressure.