Welcome to the frustrating world of the LM carby, seems you have also discovered the float needle problems. I did get some after Christmas that even though they look the same they seem to work but they are still nothing to give me any confidence. I will get some more from them and see how they go. With the fuel on give the top of the carb a tap on top and sometimes this will knock the needle out of the seat and allow fuel to flow. Give that a try before I try to explain how I modify these carbs. And at this stage you haven't come up against the [Censored] kill switch problems
