I believe that this engine is actually a Kioritz ( Echo) 21 cc even though it it is badged McCulloch. I own one too - haven't taken it apart as yet but I believe they run ball bearings.
Seems they are used on many brands, but this model is not used a lot for model aircraft for some reason ,but it certainly makes a great Weedie!
Having said that, they have been used by some with good results. Check the thread "Don't Forget Echo", you may find a lot of useful info there.