A crankshaft can have several issues, but this article addresses only one, and that is wear.
One must assume that the rod bearings have some oil to lubricate the rollers. Even with this oil, one may perform a few simple tests.
- Gently rotate the rod and feel for looseness and/or roughness. If you feel either, then it should be considered to be bad. The sideways play hasn’t been shown to be an indicator of much of anything.
- If it passes those simple tests, then it is time for a more accurate test procedure. The oil must be washed out of the rod bearings. Use a light thin solvent liberally while working the rod to assist the solvent to do its job. I like to use air pressure to clean out the solvent. Then repeat the procedure a few times. End with air pressure and a clean white rag to catch any remaining solvent. The rag should show no solvent was blown out.
- Make sure that you are in a very quiet place. Lift the wrist pin end of the rod and gently pull on it with one hand. Using the heel of the other hand give the wrist pin end a gentle bump. If you hear any click, no matter how slight, you have a problem. If this procedure is new to you, then I would suggest trying a variety of “pull” on the rod and the amount of bump. You should not find any play evidenced by a click.