Hi Chuck,
Could be a few things we might need some more info but we'll sort you out

What is the idle like while you are sitting at the lights?
Is it standard Hitachi Carb?
Have you done anything to it at all recently under the bonnet (I always like to ask that just in case)
What is it like to start?

It could well be anything at this stage / maybe some crap in the carby, or points, incorrectly adjusted accelerator pump - still just guessing a bit at this stage - need a little more info please