Hi Rob,
The 75-693 is the metering rod it should have, so I believe I'd start there first. A few things to keep in mind: we don't have the same gas as when this was designed. Today's gas isn't going to burn the same nor have the same btu rating and that's actually a notable factor. Running a bit richer with unleaded/ethanol gas is a good thing here. In Wales, I can't say because I don't know, but friends in England tell me they're being forced to use at least 10% ethanol-laced fuel. That metering rod is a stepped affair and if you want to make things more rich, you can adjust so that it sits a bit higher up off of the carburetor's floor...that is to say bend the metering rod arm to lift it up a bit. If you do this, you probably will see a change in the way it runs, but as I mentioned I think I'd start out just as that carburetor was designed.
