hi , when you say crank bearings do you mean lower end rod bearings or the crankshaft main support bearings , if you are talking about rod bearings , you check for any excess motion in side to side on big end of rod , this checks thrust washer wear , you can take the wrist pin an bearing an place in small end of rod and twist the wrist pin checking for any twisting motion in the rod , should have none to very slight ,last take an hold crank steady an an take small end of rod an pull up an push down to check for any loose movement , should have none for good tight crankshaft , if crankshaft support bearings , rotate crankshaft an feel for smoth free movement , no drag or rough feel in rotation , you can also take hold of the flywheel with both hands an try to lift the flywheel up an down checking for any loose motion or play in bearings , if no play or loose motion , bearings are ok , william anderson