Harley-Davidson VVT

Harley-Davidson plans VVT V-twin

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Harley-Davidson has filed a patent application for a variable valve timing (VVT) V-twin engine, possibly for the Sportster to improve economy and reduce emissions.

The iconic American manufacturer has often been accused of old engine technology and faced barrage of criticism for going “backwards” from double to single overhead cam with the Milwaukee Eight engine despite it being more powerful, efficient and easier to maintain.

VVT history

BMW R 1250 GS and RT VVT
BMW’s 1250cc Shiftcam Boxer engine with variable valve timing

A move to VVT would see Harley join many other motorcycle manufacturers that use the technology including the four Japanese manufacturers, BMW (ShiftCam) and Ducati (Desmodromic Valve Timing).

VVT has been around in motorcycles since the 1980s, but is surprisingly banned from MotoGP.

The first bike with VVT was the Honda CBR400F in 1983, but their Variable Valve Timing and Electronic lift Control (VTEC) only became popular in the 2002 VFR800.

Honda VFR800 VTEC engine with variable valve timing
Honda VFR800 VTEC engine with variable valve timing

Variable valve timing, which is even used in your common garden-variety Camry, makes the engine more flexible in different conditions, which results in increased fuel economy, lower emissions and improved performance, particularly torque.

Development of this technology began in the 1970s and the 1980 Alfa Romeo Spider 2000 was the production car with a mechanical VVT system.

It’s now common in cars and is known as VVT-i and VVTL-i in Toyota, MIVEC in Mitsubishi, VVL in Nissan and VANOS by Ford, BMW, Ferrari and Lamborghini.

The formula for how and when the valves open varies from manufacturer to manufacturer.

Harley VVT

Harley-Davidson VVT
Harley-Davidson VVT patent drawing

While Harley likes to keep things simple, reliable and easy to maintain, VVT would add complexity to the cylinder heads and add to the price of periodic valve adjustments.

Their patent is not for VVT which already exists, but for a modular engine balancer on either side of a crankshaft of a VVT V-twin engine.

Harley-Davidson VVT

But which Harley model would get the new engine?

The patent drawings seem to show a Fat Bob, but it has a Milwaukee Eight engine which is only a few years old, so that’s unlikely.Harley-Davidson VVT

Similarly, the water-cooled Street range engine is only a few years old and the Harley’s upcoming street fighter and adventure bikes are powered by the Revolution Max water-cooled engine.

Harley Revolution Max platform includes Pan America and Bronx Streetfighter
Harley Revolution Max platform includes Pan America and Bronx Streetfighter

This VVT engine is more likely to be fitted to the popular Sportster range whose Evolution engine is 34 years old.

It is in desperate need of a modern replacement as the Sportster will no longer be able to be sold in Europe because of tough new Euro5 emissions regulations coming next year for existing models.

Harley-Davidson Vintage Stripe Bell Bullitt retro helmet Sportster Iron 1200
Sportster is in much need of an updated powertrain

A VVT V-twin would give the Sportster a new lease on life.

While Sportster fans may be horrified at this modern tech in such a traditional motorcycle at least the drawings show air-cooling fins, so it is unlikely to have water cooling. Whew!

  1. There are a few errors in this article that may be misleading to the uninformed. The Sportster motor is called Evolution, not Revolution (two different motors). Harley’s do not have overhead cams, neither dual nor single. Sportsters have cam gears (four of them) that are spun off the crank (all of this in the bottom of the motor). The lobes on those cam gears drive hydraulicly adjusted push rods. The push rods actuate the rockers in the top of the motor, operating the valves. It’s the most reliable way of operating valves as it has no timing chain and requires no adjustment to valves, which is what makes the sportster motor superior to a big twin. I’m curious why they are going after VVT. Like most motors with push rod actuated valves, the Evo’s max rpm is limited because the valve train becomes less stable at higher engine speed. Despite having immense torque, the limited engine speeds limit horsepower. However, since the sportster has four cams, each valve has its own pushrod and cam almost directly beneath it, which is the best angle (no angle at all) for valve train stability. Changing the distance between valves and internal valve angles in the combustion chamber can be done to further stabilize the valve train at high rpm like what is done by Hammer Performance, so it is possible to safely spin those modified motors up to and beyond 8000 rpm, finally unleashing the horsepower. Harley did have a liquid cooled V4 that probably had overhead cams sometime in the late 70s or early 80s I believe. It was not pursued after the buyback from AMF and never went into a production bike. I can’t tell from this article, but I would like to see whether this VVT is in the head or if they have come up with something in the cam chest of the sportster. I personally wouldn’t care to have VVT, but I would like a counter balanced evo based sportster with higher redline, solid mounted to an aluminum frame, maybe with four valves per cylinder, inverted forks and more rear travel. With those changes, Harley could have a 450 lb bike with 130 horsepower or more. It would be a true sport bike.

  2. ……”a barrage of criticism for going “backwards” from double to single overhead cam with the Milwaukee Eight engine”.
    Oh really ! A HD with a DOHC engine. Maybe a pushrod operated DOHC ?
    (can’t count the Vrod, that’s a Porche idea)

  3. The article says “VVT would add complexity to the cylinder heads and add to the price of periodic valve adjustments.”

    I thought Harleys had hydraulic self adjusting valves and adding a VVT system probably wouldn’t change this. As a low revving engine hydraulic valve adjustment makes a lot of sense and there should not be any regular cylinder head maintenance required at all.

  4. I always thought that oil cooling around the exhaust heads would be the go – when does the current Sportster get dropped from Australian market? On another related note our cousins over the ditch in NZ are having the Suzuki DR 650 dropped due to emissions what about the market?

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