Hopefully, by now, they’ve done something about the balance shaft gear key failure. It’s a weak design, doomed to hammer itself apart over time. With it sharing space and time with the crank cheek space, when it goes it can blow the bottom off the cases, which probably doesn’t happen in a corner.
The oft maligned J motor shaft has a noisy but unlikely to come adrift gear. The Himmy one seems to be quieter and robust. I don’t know whether the RE ones are interference style or not. ??
I have no qualms about the rocking couple taming ones on 180 and 270 twins. However, the temptation to save space and weight by having the largest rotating bits kept from plowing each other by a single tooth or key failure…. It isn’t just new stuff. The DR 350 Suzukis had the gear driven by a pin, which wandered out far too often.
Despite being a traditionalist, I’ve always admired the 390 Duke. The unapologetic early ones had a certain alien insect vibe that made me think of Starship Troopers. ORANGE! Yeah!!
I’d borrow one or rent one, but ownership better come cheap.