I have only had Keihin CV40 carbs on my previous carbed Harleys and they worked well with proper jetting. I am curious if there is a substantial difference between the two?

 

I know just enough to be dangerous when it comes to carbs so thats very little. However I had a cam install on my evo many, many years ago. Way back then I was clueless how to adjust a carb but I had a independent shop and my Harley dealer work on my bike and carb and always felt like I was missing something with the CV. I had the thunder whatever it was called installed and I had the thought i'm going to stop spending money on this carb that I was not happy with so I went with a S&S and is still on the bike today.

I did learn about the S&S carb and did my on jetting, re-jetting, lots of trial and error, but after I got things set I have been happy. I was impressed with the build of the S&S, just has a heaver big hunk of metal feel to it.
As you can tell i'm not technical but I can change a jet size and turn a screw.

Perhaps early on if I had learned that stock carb better and spent the time I did with my S&S but after paying (2) shops to improve it, I was done with it. However, I remember back then as well as now that CV40 has a huge fan base and many S&S Super E haters but I always felt my S&S was a huge step up and to be honest, I wanted the S&S look and cover, to this day I think nothing looks better than that old school tear drop chrome cover...

I recently purchased the oval Harley SE heavy breather for my new M8 and thought man this chrome cover is so thin and light vs my heavy S&S cover... I guess 25 years changes a few things?

My 2 cents....

 

The E flows about 25% more than a CV40.. Whether you can use that flow depends on the rest of the motor.. You will pick up a little typically on a simple stage 1.