What's the problem?  If the starter ring gear is bad, those can be replaced.  Cut the old one off, heat up the new one, slip if in place and let it cool.  
If the flywheel is worn or heat checked, take it to some place like Auto Zone or NAPA.  They should be able to send it off to be resurfaced.  Shouldn't be very expensive at all.  I had a 100 lb tractor flywheel resurfaced last fall for $80.
If the clutch is slipping, it may be the clutch plate instead.