This is the Sachs #2.17 Atomizer aka Needle Jet for the Sachs Bing Carburetors.
For tuning tips, check out Garage. The worlds largest moped build database. Use Garage as a guide to what jet you need.
Here are some builds that use the Bing carburetor: Bing Builds
You can look at the jetting used by builders as a starting point for what you need.