Harley-Davidson is set to release a totally new engine with four valves per cylinder.
While that doesn’t seem like such a big deal – it certainly is for Harley-Davidson.
There have been seven distinct engine designs from the American manufacturer since 1914, and the company has always stuck to its familiar air-cooled, pushrod driven, two valve per cylinder design throughout.
But this new engine, the eighth in the line, is a break with that tradition and signals the beginning of a new era of technology for the company.
The new engine is fittingly called the “Milwaukee-Eight”.
There are plenty of engines with four valves per cylinder, but they’re typically higher-revving high-performance engines and usually have dual overhead camshafts.
Extra valves are favoured because they help improve efficiencies, getting air and fuel in and out of the engine easier, and increasing power and fuel economy.
Harley’s big twins use pushrod valve systems like our old V8s, and normally just have two valves on each cylinder because it’s just too complex otherwise.
While the new engine is still air cooled and uses pushrods, the increase in the number of valves will help make the new engine compliant with increasingly more stringent emissions laws.
The positioning of the pushrods – parallel to the cylinders rather than converging towards the centre of the engine – also suggests separate inlet and exhaust camshafts.
It’s capacity has been increased to 107 cubic inches, or 1753cc, and as a new engine, there’s scope to produce even larger capacity engines that would probably find their way into the CVO models.
The official unveiling of the new engine will happen late in August, and rumour has it the first bikes to get the new engine will be the touring models.