At 565 miles, the transmission fluid level on my new Heritage was barely showing on the stick and took 6.5 ounces to top it off. Whether migration or it was not filled up at the factory it’s too early to tell but I’m
going to watch it for a while.

 

Softails are 100 to 300 pounds lighter than touring bikes.
Softails don't have wet heads (and the associated different oil pumps) like some touring bikes do.
Softails have two counterbalancers rather than one like the touring bikes -- which makes the flow of pressures in the case different and may somehow contribute to less sumping.
Softails have smaller gas tanks and generally cannot run as far as a touring bike in one continuous run, meaning that enforced idle periods are more frequent on Softails, which may mean not as much oil has a chance to accumulate as it would on a touring bike.

None of these factors seem like they'd affect sumping that much, but when taken all together in aggregate, it adds up to the Softail rarely if ever sumping.

Most importantly, Softails aren't CVOs with Stage IV kits put on them -- those are the most likely to sump and grossly disproportionately make the rest of the M8s look bad. I think if Harley would have never released the Stage IV kit, we'd probably never have heard about sumping. It still would have happened here and there, but it's the CVO/Stage IV guys who harp the loudest (and, fairly so, since they spent $50,000 on their bikes).