You need to open the engine, remove the crankshaft and have a feel on the bearings with your finger. That is ultimately the only way to know for sure.
Most people are really afraid to open the engine, but it is nothing to be afraid of.
Just rotate the engine to where you know the piston is near top dead centre.
Then remove the four screws on the back plate, and carefully remove the back plate, and off you go.
It's not scary once you get going!
Then stick your finger in the bearing, and rotate it.
If it feels gritty, like it has sand in it, you need a new bearing.
And in any case, it is better to be safe than sorry! So just get some nice ceramics