It seems obvious now that if the engine was designed to run with one carb, it's not going to run well by bolting on another. Same with the linkage - the spring could shut off the throttle when the carb was above it but with a carb on either side of it the spring hasn't got the power to pull them both down properly. I read all the technical info and the Langdon article but unless you're a real carb expert you could get into an awful mess trying to adjust the carb without really knowing what you're doing. What surprises me is that the dual carb set-up is so popular you would think there was a definite way to get it to run well, such as a fuel pump limiter, if one exists. Maybe the bigger jets would work - when I got the new carb it had a 58 jet, so maybe that might help. Thanks for your help - I'll keep experimenting with it.
