Experts and BHG readers answer.
Cherry Trees with cherries the size of bb's?
It's possible that the grafted variety (sweet or sour) died back and that the tree you have is coming from the rootstock, which could be like a wild cherry. The size of fruit that you indicate suggests that may be what happened. You won't be able to get the tree to produce larger fruits than it is genetically programmed to grow. You may need to replace the tree or graft on a commercial variety to get desirable fruits.