My engine is suffering from a flat/sickly spot when you start to lift the revs from idle, then it passes once you increase the revs. I'm finding it really annoying as you have to keeps the revs up all the time in town, which isn't really my style of driving. It's an AB engine and the valve clearances and timing have just been checked/adjusted and the fuel set according to the Bentley manual. It's a Bocar carb and is fairly new. Any advice would be greatly appreciated.