I'm using good quality front wheel bearings from http://www.gokartgalaxy.com/bearings.htm
there number #8273 and only $5.95 sealed both sides. I'm using these on all my cadets going on two years now.
These are the same quality bearings that IH uses but there sealed on both sides. I find that water and rust is the main destroyer of these front wheel bearings so I think the sealed on both sides may last longer. The grease is captured.
I have seen one of my cadets have the sheetmetal stamped ball bearing in it too but its not really sealed that good it looked like new and it was shot too.
I also had to replace the rims too because of the bearing going bad and it eats into the rim. The PO just ran them anyway.