Push comes to shove: Harley-Davidson patent reveals VVT pushrod engine
Harley-Davidson have patented a variable valve timing (VVT) system for their next engine in a bid to meet emissions targets for an air-cooled engine.
This isn’t the first time we’ve seen drawings for this unit, which breaks with Harley tradition by placing the pushrods either side of the cylinders (Harley have run four pushrods on one side since 1930, so swapping to two per side is a massive change), but it is the first time we get an inkling for what it might be for.
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Despite many believing Euro5 will spell the end for air-cooled motors, there are still plenty around – just take the new BMW R18 as the perfect example. Low-revving motors aren’t a problem for Euro5, it’s the high-revving ones that are challenging, so this new VVT system will make the most sense on a smaller capacity, higher-revving bike; something like a new Sportster.
But how does the new tech work? The new motor will use an oil pressure actuator to shift the mechanism, phasing the action of the cam. The principle is very similar to Ducati’s variable valve system on the Multistrada. What’s different about this, is that the system runs off an intermediate gear, meaning it spins in the opposite direction to the crankshaft.
To balance out vibrations, Harley have added a balancer shaft, which rotates against the VVT system. It’s quite nifty, although it is rather complex and could be expensive - the opposite of what Sportsters are meant to be.
We imagine the new design will find its way into Harley-Davidson’s smaller Sportster range where it could unlock higher horsepower figures to compete with new bikes from Indian and Triumph and given that the Euro5 deadline is fast approaching, it might not be long until we see it in the metal.