All three FEs are brand-new from the ground up. The radical “upside-down” engine is gone, replaced by conventionally oriented units that Husaberg claims outperform the previous motor due to advancements in technology and reduction in weight and reciprocating mass. They all
are four-valve, counterbalanced Singles that share die-cast crankcases, fuel injection with 42mm throttle bodies, Keihin engine-management systems and electric starting. A key difference between the 250/350 and the 501 is the cylinder head: The latter has a single overhead cam with rocker-arm actuation, whereas the 250 and 350 use double overhead cams with finger followers and titanium valves.