Problem solved!!! Sheepishly I admit I didn't do what is often suggested as the first steps right away. Yesterday, I finally took the long drive to town and got new plugs and fuel filter. I found the filter quite clogged and one spark plug had two good cracks in it. Did these replacements, took her out and she runs as smooth and fast as ever! So relieved!!!

Thanks z28ke, I did take a look down the carb and with the lever all the way down the secondary plates did not open. So I am taking this to mean my carb is vacuum controlled.

Thanks to all of you for the thought and help. Sorry, I wasnt smart enough to take the correct first steps before jumping to more drastic conclusions. This is a great forum with terrific readers and contributors.