Question
Locust tree..15 years old...has lots of dead limbs..main limbs look fine..but tree is getting very bare..and leaves..not as bushy this year...had lots of blooms and droppings..likeit was healthy..

I think it is a honey or sunburst.not sure...

Answer
Yes it sounds like the trre could use a cleaning pruning to take out the dead limbs. The best time to prune honeylocust is September and October. I would recommend fertilizing the tree with a 20-10-10 fertilizer and go ahead and prune ONLY the dead limbs now and in September prune any others that need it. Here is a web link to information on how to prune trees and also fertilizing.  http://www.treesaregood.com/treecare/pruning_mature.aspx
http://www.ext.nodak.edu/extpubs/plantsci/trees/h1035w.htm