I pulled my intake apart to verify the differences of the Honda Express reeds and this is the low down. The larger one is for an ‘83 Urban Express (not sure if it’s something special like Iowa or something) and does NOT fit the opening in of the Express 2-speed cases. Although, it could be fit with some minimal grinding. You can plainly see the significantly larger size (approx 15%). The direction of flow is more desirable following the rotation of the crank and there's a even a minor reduction to crankcase volume (stuffing) with the angled valve position in the cases.
For complete video of this and other mod variations, search You Tube: Extreme Urban Express reed valves
Or, search You Tube: Routabit - for all videos related to Honda Urban Express tuning mods