Replace vacuum tubing. Clean the carb properly with full disassembly. There's really no short cutting a good carb cleaning. One of the (3... 4?) internal rubber seals inside the carb may have failed. Is the petcock leaking? Does the tank vent properly? How do the plugs look? Does the battery test well, and I don't mean for 12v, but rather if you load test it what's the result?