I have a 81 cb 750 f which is hard to start after setting more than a couple of days. I can place a flat piece of cardboard on the carbs (as a choke) while cranking and the fuel gets to the engine much quicker, or starts easier. The Choke butterflies are adjusted properly, I think about the Triumph MCs that had a bleeder button on the float reservoir. On the cb750 f there is an air cutoff valve which I donĀ“t fully understand. Is there something that I have neglected to check that is over regulating or restricting the fuel supply?