Honda rotovator/tiller wheel ballast?

I have a honda heavy duty tiller/rotovator which has steel weights fitted to the wheels. The tyres are not inflated and I understand that they can be waterballasted.
My question is,should these tyres be inflated with air when they are used without water ballasting, or should thay be run flat??? (The previous owner has been using this machine for several years without inflating at all!!) You can imagine how difficult it is to turn this round with the tractor type tyres.