Cap jet
When installed with a gasket washer, it's tip should be level with (to 1/16" below) the lower casting shelf that the Venturi sits on.
Main jet
When installed with a washer, its tip should be level with the Lower Casting shelf that the Venturi sits on. So, when you remove a Main Jet, make sure you also dig out the old gasket. If you end up with multiple gaskets installed, it will cause poor performance and leaks, because the Jet tip isn't precisely where it should be in the Venturi.
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http://www.modela.org/components.html