How to motivate team to work on legacy products

We are a team working on legacy code which is pretty old and written in languages of initial programming days. As the team members are trained in latest technology and are now put to work on legacy code, they are not happy. How to motivate them to work in legacy code also?

Send your team to meet users and watch them use software. They should find out what are most critical problems users have with that software.

Getting to know users makes work more real - your team will know that adding new functionality or eliminating some bugs will help some real person. That should motivate programmers to get boring job done.