made a mixture mistake... any suggestions?

I believe that the correct mixture for break-in is 1 gallon of gas to 8oz oil. You basically ran the engine lean. If it was too lean than that could have ruined the engine. I usually run the 1gal of fuel to 4oz oil mixture on broken in engines with no issues, so there should not be any problems with the actual engine. The carb might have been tuned for the richer mixture and now needs to be re-tuned.

8 oz. of oil per 2gallons is 32:1 is a recommended mixture after break in

When your breaking in you wanna run just a bit heavy on the oil to get everything nice and lubricated.

But your engine should be okay still

What color is the spark plug? The engine must be completely cool to the touch before removing the spark plug or you risk damaging the threads in the cylinder head. If it is black, try raising the clip on the slide needle 1 position. This allows the needle to drop down further and reduces the amount of fuel added to the incoming air (leaning the state of tune). Note that this only affects the tune from 1/8 throttle to 3/4 throttle. If this helps, ride it for a while and check the color of the spark plug again. You are wanting a chocolate to leather brown color.
If you are having problems at throttle positions above 3/4 throttle then you need to re-jet the carburetor.

One notch eh? Yeah, I have read about those. That sucks... performance without the ability of fine tuning it. Sounds like an oxymoron.
I have read of folks using the needle out of an NT carb in your carb with sucess.
Here, bottom left side: Carb needle.