TR6 - Carb rebuild - when?

[Richard.R.Olson@tc.faa.gov (Richard R Olson)]

     Hello again,
     
     If I remember correctly the ZS carbs should be 'rebuilt' after 20 
     or 30K miles.
     
     How do you determine whether the 'rebuild' should be the 
     easier/cheaper new diaphragm/needle/gaskets, etc kit that can be 
     done by the owner
     
     or the new throttle shaft/seals full blown and $$$ rebuild, usually 
     done by a carb rebuild shop?
     
     I am seeing the remains of fuel on the outside body of each carb 
     (no visible 'wet' fuel, just the gunk that remains after fuel has 
     dried).  The carbs were externally cleaned about 4 years/15K miles 
     ago, but no other work has been done on them.  The car still runs 
     fine, although it does 'hunt' at idle a bit.
     
     TIA,
     Rick Olson