Well if the bearings are bad the engine can run irratic, be difficult to tune, have strange sounding noise, leak badly out of front bearing. Also they can be bad and not cause any problems that you can notice. Like if If they feel gritty and not smooth, And if there is to much play or slop in them allowing the crank to move around.(it doesnt take much)

If you like just send them in and we can check all the tolerances for you. Sometimes it can be hard to tell if your not sure what to look for.

Thanks,
Lance
RcRenew.com