Considering that the inlet diameter for the boyesen reed cage is 35mm, would you see any benefit from having a carburetor that is any bigger (36-39mm)? The way I see it is, you still have a 35mm bottleneck impeding your airflow at high RPM, and a decreased airflow velocity in the wider carb's venturi hurting your low RPM performance. Yet, a lot of ppl go big on the carb size (myself included). What am I missing? Are there other reeds with larger inlets?

Any point between the carburetor and the reeds that is smaller than the carb will make the engine think that the carb is the size of the restricted area.  Large carbs on restricted manifolds or reeds can make carburetor tuning difficult or make the carburetor very temperamental to temperature and altitude changes.

The intake manifold is the most common area of neglect by the aftermarket carburetor sellers.  The majority of the engines I modify have big carbs with stock intake manifolds.  Most stock intake manifolds were made for the stock carbs and restrict the flow of the larger carbs.  The transition shape from the carb to the reeds is important.  When the shape is not right a larger carb may not make any more power than a stock carb.


Putting the correct exhaust system on your engine will have a much more dramatic effect on you low end power or shape of the power curve than carburetor size.