How important are smooth bearings?

In my work selling model engine collections, I've encountered a number of engines that have a slight roughness in the bearings.  This has been with various engines, and is not specific to a brand.  Super Tigre, O.S., Ross, etc.  Though I do my best to note this to buyers, I've had at least one engine returned.

I suspect the cause of the roughness, what you might call a "notching," is rust or possibly even congealed oil.  Often it disappears when the engine is warm, returns cold.

Recently I've been evaluating an O.S. SF 46 with the standard R/C "SF" crank timing.  It has a slight roughness in the bearings.  Yet, it starts and runs great, based on test stand runs.  Should I be concerned about the bearings or just run it?

thanks,

Peter

bearings are cheap but dont use cheap bearings. most older motors have been run on mostly caster based fuels and if not run for a length of time the bearings will gum up.newer motors that have been run on synthetic oil ,the bearings can rust up if after oil is not used.
  i feel that any motor that has not been run for a year or more should at least have the backplate removed and any crud flushed out and the rear bearing inspected and flushed out with carb cleaner or some other solvent.S/T rods seem to stick to the wristpin then all the wear is on the wristpin and piston.
  most cheap bearings are made with a brass bearing retainers ,after time the tabs can break off and go through the motor doing major damage. better bearings have better retainers that should last the life of the motor.
 a long storey but i have real life proof that Japanese bearings are superior to Chinese bearings

   

Never  run an  engine  with  rough  feeling  bearings, the  bearings  will  shed  small  parts  of  whatever the  roughness is....  rust, solid dried oil, corrosions  etc, and  then  it will  run thru the  piston and  sleeve

Randy

Running rough/pitted bearings is rolling the dice. If you wait too long before changing bearings it destroys the engine. I had it happen on a Kraft 60 while on the test stand and took about one second to go from smooth running to massive vibration and a full stop. Case, crank, piston, rod, liner, back plate, head hammered to death and BOTH bearings in pieces.

multiple bearing types for just about ant engine. been using them for years and not just for model engines.

https://www.bocabearings.com/?gclid=CjwKCAjw4MP5BRBtEiwASfwAL0sTWtcDLGrEdypTidEamu48GGv9csmm3wTqaYKmkIUB-uJGxzIqbBoCNsgQAvD_BwE