I like my bike as smooth as possible.
The balance shaft was invented by a Brit
named Lanchester in 1904.
The shaft takes care of the second order .
The manufacturers would not spend $ if they
didn't think it was necessary.
I like smoothness, as well...but not too much. I don't want my motorcycles to become dull anonymous modern appliances. If I wanted dull and anonymous and modern I'd be riding something like a Husqvarna Svartpilen or a BMW F650.
The thought of an 800cc, carbed, air cooled thumper makes my heart sing, but I'm not willing to be naive--while my heart is singing my head is wondering just how much vibration I would in REAL LIFE consider too taxing to enjoy beyond a half hour.
A DR650 engine can be bored up to 790cc, and then stroked up to 900cc if so desired, and of course that engine has been counterbalanced since its inception in 1990, so the potential for huge hot rod power is well documented while still maintaining reasonably low levels of vibration.
But as terrific as the engines of the Suzuki DR650 and Honda XR650 and Yamaha XT660 are, with their overhead cams and four valve heads and compact dimensions and counterbalancer assemblies, none of them quite strum a luddite's heart strings like the raw thunder of an even older school pushrod two valve head Royal Enfield 535 or a Sportster "halfster" 800.