ORIGINAL: asmund
I now understand you Kostas, but manufacturers don`t use BALL bearings in those places, but rather NEEDLE bearings. As a general rule only gas engines has bearings in those places (both ends/holes of the con-rod) There`s some exeptions and as mentioned some MVVS glow engines also utilize needle bearings in the rod. Just google and you will find out just what a needle bearing looks like
Asmund now i got it!
So the part that provides this friction-free ,spin, is not a ball but needle-shaped part.
Why these needle-bearings in such areas as the conrod,
are used only by few manufacturers.
I don't think it is the cost of parts.
And that assembly could give far better operation and smothness.