Classic Techniques
This is about tuning a Goldie, a 1957 DBD34 in American road trim. But it’s not a story about tuning a fire-breathing monster to extract every last horsepower; it’s about tuning a road bike’s carburettor for rideability and good manners. Those of you who think that a Goldie should only wear a GP carb should look away now, because the carb in question is an Amal Mk1 Concentric, a 1036 with 36mm bore. This carb probably started life on a large Spanish 2-stroke because these and the Velocette Thruxton were the only models to which they were originally fitted, and the carbs are no longer made.
Why a Concentric? GP carbs don’t have an idle circuit which makes them difficult to ride in traffic, even the relatively light traffic that we experience in New Zealand. Plus they have a reputation for being beasts to start.
My aims for this project were easy starting; the opportunity to fit an air filter (I’m going for long engine life); reasonable top end power, recognising that I will seldom ride much over the speed limit of 60mph; smooth operation across all practical rev ranges which I define as 2000-5000rpm. Sure, I might occasionally go higher than this but not as part of my regular riding. The bike is used for club rides, rallies and local trips. I considered a Mikuni
