So if you noticed watching each model year, 18s have the standard primary cover with the standard derby cover size that harley's been using for a while.
However, when the 19 model year came around the MOCO started using a narrow primary cover with a smaller sized derby cover(much to my dismay because there were a lot of really kick *** derby covers I was looking at for customizing and none of them fit on the 19 and 20 primary now.)
The narrow primary cover debuted on the 18 sport glide, but all of the current softails have this narrow version.

Now I'm wondering here... Why would harley switch over to a narrow primary cover when the 18 was just fine, and tons of PnA and aftermarket derby covers and established parts all worked with it.
Why go through the process of making an entirely new sized part that requires a new setup, unless it was meant to deal with something that was an issue with the M8 engine... EG the Primary transfer issue?

Am I barking up the wrong tree here? If not, should I buy or replace the wide primary cover with the narrow one when I get the bike?
Also do you think Roland Sands might make that cool see through derby cover for the narrow primary cover? I had my eye on that one.

 

No transfer that I know of with the softails. If you wanted, you can purchase the wider primary. I think the main reason for it is leg clearance when stopped. I know my leg is up against the primary when I stop and put my foot down.

It's just the natural place I always put my foot down at and if I don't think to move my leg away from it I always end up with my calf against it until it gets too hot and reminds me to move my leg and have a wider stance at a stop. Not sure though so maybe someone who knows more about it will chime in.

 

I don't know that the 19's and 20's come stock with the Narrow Primary Cover.... I could be wrong but I believe this is still only an option through HD P&A. I bought a '19 Slim and have a standard HD Derby Cover ordered through my dealer for it. I know it's a standard and not the narrow Derby Cover because it is the Brass Collection one and they do not have a Narrow Brass Collection cover.

I'll let you know if I get it and the Dealer just wasn't aware that this won't fit, but I'm hoping they would have alerted me to this when I ordered it. Additionally, it is an option with my model year bike selected on HD.com so I'm thinking that the bike comes stock with the standard primary.

Hope this helps, I'll follow up with you on the Derby Cover when I go to install, this should answer our question.

 

Agreed, I believe this is all still due to leg clearance as I believe it is just an option through parts and accessories.

 

The narrow primary came in 17 on the touring bikes. More leg room nothing to do with venting

 

2016 was first year for narrow outer primary cover on touring bikes.

 

Also saves some weight and looks cool....Especially on my Slim.

 

It adds some ground clearance for lean angle too.

 

And one more time for the record...transfer does not relate to the Softails. Transfer relates to the touring models hydraulic clutch system only. The Softails have a traditional cable clutch...no fluid transfer is occurring on these models.

 

Looking at HD's website... The new Softails do appear to be sporting the narrow primary cover.