For the stumble, set your accel. pump rod higher on the drivers' side front of the carb. Pop off the little O'Jesus clip.....DON'T lose it, slide out the linkage and move to next hole. Mine had this problem until I moved it up. Read spark plugs to determine what it is running. Look in most Chilton's manuals for a color chart. White is too lean, black is rich, brown is about right.
Nah, I popped one of my witewalls doing the autocross and had to roll on a blackwall the rest of the weekend.