Vintage BMW Motorcycle Owners

I am getting conflicting information on the 40mm Bing carbs vs the 38mm Dellorto carbs as furnished on the R90S. Anybody know if the 38mm Dellorto's have as much performance capacity as the 40mm Bings? At first glance the smaller throat size in the 38mm Dellortos should have less capacity to flow air but as with most things this may not be the case. The butterfly shaft and throttle plate in the throat of the 40mm Bing's may actually be more restrictive as opposed to the open unrestricted throat in the 38mm Dellortos.

My understanding/experience is for the most part the Bings and Delortos are neck and neck for performance except the Delortos have an accelerator pump in them whereas the Bings do not.

So you get a bit more bang for the buck with the Dels on acceleration but that is about it. St.