Compact, lightweight and powerful describe Piaggio’s new 350 scooter engine more precisely than you might think. In fact, this little Single proved so incredibly efficient during my recent test ride that it became the “main character” of the event, making the Beverly Sport Touring model that it powers secondary to the story.
This new engine actually displaces 330cc and generates a claimed 33.3 horsepower at 8250 rpm and 23.8 foot-pounds of torque at 6250 rpm. Both are excellent numbers for such an obviously under-stressed though clearly highly efficient engine. To achieve these brilliant results, engineers selected mildly oversquare bore-and-stroke measurements, 78.0 x 69.0mm, and a not-so-mild 12:1 compression ratio. The engine breathes through a 38mm throttle body. Inlet valves have a diameter of 28.4mm, exhausts are 23.2mm, and they are set at an included angle of 33 degrees.
The shallow profile of the upper half of the combustion chamber carved into the cylinder head is complemented by a dished piston top for a clean “semi-Heron” combustion chamber. The comparatively small diameter of the four valves allowed engineers to crop them at the center of the head, leaving room for an almost perfectly annular squish band that further increases the already very good thermodynamic efficiency of this unit.
A curved, trumpet-style inlet runner was selected to induce a strong tumble effect in the inhaled charge, right from the lowest possible rpm, for a flat torque curve. Obviously, this choice limits volumetric efficiency at high rpm, but the Piaggio specialists never intended this unit to rev past 10,000 rpm. The curved runner was also selected to help create a compact package that could easily replace the smaller-displacement engines currently in service.
For the same purpose, a 110mm connecting rod was adopted, resulting in a 1.59:1 rod/stroke ratio. Accurate counterweighting was important to keep the primary-imbalance-generated vibrations to a minimum, since there was nothing that could be done about the secondary imbalance consequent to the sub-2:1 rod/stroke ratio. The crankshaft is the pressed kind, turning on plain bearings at both main and crank journals, and accurately and solidly assembled through a procedure developed by Piaggio that prevents risk of misalignment, flexing or twisting. No balancing shaft was adopted, but an elastic mount effectively isolates the vibrating engine from the rest of the scooter. To reduce losses due to fluid drag, the unit uses a dry-sump lubrication system.
Piaggio’s 350 also has a completely new transmission, albeit a tried-and-true CVT automatic. Here, a new oil-bath, multi-disc clutch replaces the traditional centrifugal-shoes kind, while the V-belt only needs to be checked every 12,000 miles, like the rest of the engine.
This little jewel of an engine was first fitted to the new PiaggioBeverlySport Touring scooter, replacing the much-heavier 400cc unit—a real gas-guzzler producing similar power. The Beverly Sport Touring weighs 390 pounds, 44 less than theBeverly400, and returns 78.4 miles to the gallon. Given a fuel-tank capacity of 3.4 gal., theBeverlyshould go 266.5 miles before refueling is required.
And it really goes! Top speed soars past 90 mph, and acceleration and throttle response are brilliant. The new clutch is smooth, snatch-free and precise, and the whole Beverly Sport Touring is more comfortable than previous versions, thanks to a windshield that is compact but effective.
I rode the Beverly Sport Touring through a drizzly, wet day, and the only drawback was my ballooning lightweight rain jacket. My particular Beverly was fitted with the optional Brembo braking system, complete with ABS that also doubles as ASR traction control. Despite the slippery road, the fat tires (110/70-16 front and 150/70-14 rear) offered plenty of grip for safe cornering. The slightly reduced steering angle and lighter weight of the machine extract extra agility from the chassis. That, too, was appreciated, since it did not limit the traditional stability of this elegantly designed scooter that now features possibly the best and most-efficient engine in its class.
The Beverly 350 Sport Touring will come to the U.S. as the BV 350 in March, 2012, as a 2013 model. MSRP will be $5399. It will be available in Matte Silver or Black.