Re: Fuel in oil - where to start?
"send the carb off for rebuild"
That would be like expecting your local stock broker to outperform Warren Buffet. Ain't gonna happen. In my limited experience, there are two kinds of carb rebuild shops. The ones that charge a bloody *ing fortune, and the ones that do the job cheap and fast, and neither one does it well.
This is one of those "if you want it done right, do it yourself" jobs. Requires a gallon of gumout (for soaking), a patient afternoon, and a handle of common tools, drill bits or wire gauges, and not any special or expensive things.
Look into buying a "major rebuild kit" for your carb, and check out what's involved in the overhaul. Any library should have reference books that will show something similar, if you cna't find it online. With a digicam to take quick cheap pix to remind you how things get stacked back up during reassembly, you can probably save $200-300 over the cost of a competent rebuild. Which some of us would call a fair rate for an afternoon of quiet work at a table.
Carbs generally should be rebuilt every 5 years or so anyway, since the rubber bits don't like the gasoline and the gasoline would rather turn into varnish and plug up all the passages by then anyhow.