John , your problems I would say are Carb related. From memory the float level is not adjustable , the needle being fixed in the float , so I’m not sure what adjustments you have made.
Before going down the valve route(which I have strong doubts are not your problem) , firstly THOROUGHLY clean the carb , try it again , if problem persists , raise the slide fuel needle slightly and try again.
Be VERY careful when re-assembling , it is very easy on these carbs to damage the top of the float needle , check this on yours , they have an extremely fine tip , and the slightest damage will result in flooding issues.
Andy.