Sem minibike

Sorry, this is a two(ish) wheel request,

The front wheel bearings in our family Sem MiniBike (MB) have collapsed .

Apart from buying another complete wheel. Does anyone know how to
replace/dismantle the bearing and replace the bearing shaft and the
bearing cage. Ours has a plastic cage and seven 3-4mm bearings. The
bearing shaft was (intentionally) in two parts and appears to be an
interferance fit.

In our defence however, Adam (my son) does wheely the MB, so consider this
a request from a Mini-Uni Recumbent rider. He has however been brought up
appropriately and also rides a MUni, or Giraffe, as should all teenagers!

Duncan & Chris, (Unstable & Unable)