I have a 1973 CB750. I have recently ran into a problem in how it acts like it is not getting enough fuel. I can start riding and it runs fine. Starts right up and purrs for awhile. Then it starts acting like it is not getting enough fuel. Sometimes it will run like that for a short time then go back to running fine. Other times it will run like that till I get home. Usually after setting overnight it will start right up the next day. I tried switching to a electronic ignition and although it does seem to run better when it runs it still acts like it is not getting fuel. Any ideas on what could be the problem?