I had a rare 'breakdown' on the way to the Gold Cup yesterday. Car began misbehaving and wouldn't tick-over. Then when I smelled fuel I decided to investigate because of the fire risk. I had an extinguisher in the car and also I'd decided to avoid the motorway thank goodness. Well I soon realised that the needle valve on the rear carb was the problem but 'tapping' the float chamber didn't cure it. Fuel was dripping onto my enlarged heat shield. Annoyingly on my carbs the cover on the float chamber won't lift off without moving the float chamber sideways. That meant I had to remove the carb to get at the 10mm nut that is hidden behind the linkage to the main-jet. I didn't know about that nut until yesterday. Undid the air-filter and about a pint of fuel poured out! So the reason for the post is to highlight the difference between the 3 screw and 4 screw dashpot designs and how to remove the float chamber cover. Mine is the earlier 3 screw carbs. Also carry an extinguisher just in case of fire. I cleaned the needle (it's not one piece but two and a tiny spring) and then it was sorted.