Gas range valves

Can the burner valves on a gas range be cleaned or rebuilt? I have two on my stove that are really sticky and very difficult to operate.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.