RE: Nelson 40 ss air leak?
You need to take the spray bar out and clean it. If you don't want to do that, at least remove the needle
valve and pump fuel through the spray bar. Than plug the needle valve hole and pump fuel again, and
observe if a steady stream of fuel is comming out of the hole in the carburetor or venturi. If you feel resistance there is a good chance the spray bar is turned so that the hole in the spray bar is no longer
lined up with the hole in the venturi. My engines are older, so I don't know if there have been design
changes. If this hint applies to your engine, you will know from my description what to do.
Here's the tip: every Nelson spray bar that I've ever see has the hole exactely lined up with one of the 6
points on the wrench "hex". Mark that hex and reinstall the spray bar making sure that the "hex" point
is pointed directly into the matching venturi hole. Good Luck, Greg