May have found the carb issue with Mabel. I took the carb apart last night to clean the jets and tested the float. However, I tested the float in water which is heavier than gas, so it floated fine in water, but as you can see from the pics above, it doesn’t float in gas. These floats are notorious for absorbing gas over time and becoming too heavy to float. In the video below, you can see how rough it’s running and gas coming through the bypass. It’s not being cut off, therefore flooding the carb. Hopefully a new float will solve the problem.
Replaced the float a few days later. Back in business!