Crank bearing with 10 balls?

[1976RD400C]

I started checking out a 400 motor I bought a couple years ago and noticed it has crank bearings using 10 balls and no pips to prevent then from rotating. There are no numbers on them. Everything seems good with it. The rods are within spec and the bearings feel great. I think the OEM bearings use a 7 ball for the outers and 9 for the inners. Any opinions on why someone did this?

[rodneya]

Probably max load bearings as an upgrade to stock 7 ball. Some people think the 10ball  create too much drag, so they use the 8 ball.
Manufacturer is important because most max load bearings are for load, not high rpm. Something like KOYO can handle the RPM of even modified motors though.
Are there o rings on the bearing to stop it spinning in the case?

[2 Stroke Jamoke]

I used a max load 10 ball bearing on the flywheel side of my crank.  It is only really needed on that side because of the weight of the spinning flywheel

[Dvsrd]

I used a max load 10 ball bearing on the flywheel side of my crank.  It is only really needed on that side because of the weight of the spinning flywheel

Try dividing crankshaft torque by the effective radius of the crank primary gear. On a RDAC, torque is 37 Nm IIRC. Gear radius is around 1 inch or 0.0254  m.  That gives a force of 1457 N or 327 Lbs. Which is a lot more than the weight of a flywheel or alternator rotor.
I believe TZs have a stronger (roller?) befaring on the primary side.

[1976RD400C]

Probably max load bearings as an upgrade to stock 7 ball. Some people think the 10ball  create too much drag, so they use the 8 ball.
Manufacturer is important because most max load bearings are for load, not high rpm. Something like KOYO can handle the RPM of even modified motors though.
Are there o rings on the bearing to stop it spinning in the case?

There were no O rings. Anyone know what thickness the O ring needs to be to fit the bearing groove properly and not hinder the outer race from seating in the case properly?

[Striker1423]

Probably max load bearings as an upgrade to stock 7 ball. Some people think the 10ball  create too much drag, so they use the 8 ball.
Manufacturer is important because most max load bearings are for load, not high rpm. Something like KOYO can handle the RPM of even modified motors though.
Are there o rings on the bearing to stop it spinning in the case?

There were no O rings. Anyone know what thickness the O ring needs to be to fit the bearing groove properly and not hinder the outer race from seating in the case properly?

The O-rings on my Vito's crank just fit in the groove. They aren't super hard. I'd suggest just finding one that fits the groove and outer diameter snuggly. The clanking force of the cases will crush an o ring easily.