As I understand it there is zero way to revive those metering units and they should be considered consumable, expect to replace them. Do they have a tiny filter and a check valve, no way to back flush the filter?
The surface grinder we paid $240 for and had little over $650 in it after cleaning and replacing and fixing what it needed, not really a restoration or rebuild just a serious tuneup.
The Bijur parts are not quite cheap but they are necessary and straight from Bijur was as cheap as I could find most of them, and they were easy to work with and very helpful folks.
