I have a 1978 Honda CB550 F2, it runs very rough at tick over, when i rev it, runs at high revs for about 30 seconds before it slows down and then runs rough again, one of the carbs keeps flooding, I have changed the needle valve and set floats but it still does it, points and condenser have been changed, it appears to over heat when I take it on the road and looses all power. Anyone any ideas on how to cure it.