1000 hours is 50,000 miles at 50, I have seen the jets clog up in 1 hour of operation with no aircleaner, this is the airbleed jet, the orfice is small, just a piece of leftover gasket fuzz from manufacturing can get stuck in it, I have had to clean them before delivery of a new car, the idle will be poor, turning the mixture adj screw all the way out seems to almost fix it, I don't use this carb on my A, I like the ease of cleaning the original Zenith---1 bolt, and the jets are large enough to pass almost all that can pass the screens filtering the fuel.
All weber carbs don't like dirt, have small passages and like to get dirt in the idle passages ---I am not saying that the weber is a bad carb, the one used on the A was in it's many similar forms on many 70s cars, fiats, fords, renaults --pinto, capri, aftermarket conversions ---whenever there is an idle complaint start with the idle air bleed, then try to dislodge other debris with a spray of carb cleaner in the hole before taking the top off to do a more complete cleaning was how i approached the problem ---some of the 70s cars had a electric solenoid to shut off the jet to prevent runon --diesling.
