S&S Cycle X-Wedge Engine - First Look

Here at HOT BIKE, we strive to stay on top of the most innovative parts to hit the American V-Twin industry, so we're bringing you a new tech piece entitled "First Look." With this series, we will search out the newest parts and get you the inside scoop on what they are and how they work. Then we will follow up in a future issue by actually installing the part(s), explaining the install process, and giving an evaluation.

S&S Cycle, of Viola, WI, formally unveiled its all-new X-Wedge engine earlier this year at the Cincinnati V-Twin trade show. S&S President Brett Smith said, "We wanted to do something completely different and off the map." And something completely different they surely did. The new engine, dubbed the "X-Wedge," is a 117ci air-cooled pushrod V-Twin with an emissions-legal fuel-injection management system. Smith went on to say, "The 45-degree V-Twin is rather old technology and creates limitations."

Code-named "Fred" by S&S engineers, the X-Wedge program began in 2002. Design goals for the X-Wedge engine were to solve problems that have plagued earlier V-Twins while adding innovative functionality, simplicity, and ease of production. Moreover, S&S wanted to ensure compliance with future worldwide emissions regulations. If you are the owner, rider, or builder of an earlier V-Twin, you probably are aware of traditional problems such as wobbly and out-of-true cranks, undue camtrain wear and noise, oil puking, overheating, and excessive vibration. S&S addressed these and other issues with their new, fully EPA-compliant X-Wedge engine.

The new X-Wedge engine is a 117 cubic inch displacement (4-1/8-inch bore x 4-3/8-inch stroke), 56 degree (actually 56.25 degrees), air-cooled, pushrod-valvetrain V-Twin. It has a belt-driven 3-cam layout, one-piece forged crankshaft, automotive-style two-piece rods, and closed-loop fuel injection. The new engine accepts the standard V-Twin charging system and common primary drive components, but has unique engine-to-chassis mounts for additional strength. Since X-Wedge cylinders are designed to accommodate bore sizes from 4.125 inch to 4.375 inch, S&S will be offering additional engine combinations and Hot Set Up Kits.

The foundation of any quality engine is a stout bottom end. As such, S&S departed from the traditional three- and five-piece V-Twin crank and designed a forged, one-piece crankshaft. Connected to single 2.2-inch crankpin are automotive-style two-piece connecting rods arranged side-by-side. Instead of riding on needle bearings, the I-beam rods run on plain bearings lubricated by oil fed at up to 80 psi. The pork chop-styled Nitrated crank includes a series of elongated holes on the right-side half that a crank position sensor reads for the engine's electronic management control. At 43 pounds, the new crank is roughly six pounds heavier than an S&S Evo-style crank. The extra weight is intended to help reduce vibration.

Supporting the pork chop-style crank is a robust crankcase with offset cylinder spigot holes, simplified oil control system and improved engine mounts. The offset spigot holes are necessitated by the side-by-side rod configuration. Crankcase cylinder angle is set to 56.25 degrees, versus 45 degrees for earlier V-Twins. The wider cylinder angle, when combined with a higher case deck height, allows larger bore sizes without having to notch the piston skirts for clearance when the pistons are at the bottom of their stroke. A wider 56-degree cylinder angle also results in a more self-balancing engine than a narrower 45-degree angle. X-Wedge crankcases are designed to accept standard primary drive and transmission components. S&S offers their own six-speed gearbox and heavy-duty clutch components for big, high-torque applications. X-Wedge engine mounts are beefier than stock units and use 7/16-inch bolts instead of traditional 3/8-inch items. To eliminate undesirable performance compromises, X-Wedge case mounts are designed for aftermarket frames and will not fit in a standard frame. Currently, no less than three aftermarket chassis manufacturers are currently offering frames for the X-Wedge engine.

Lubrication is provided by a new dry-sump oiling system utilizing a gerotor pump internally located in the right-side cam case and driven by the crank's pinion shaft. Used oil is eventually collected in a common sump at the bottom of the cam case and returned to the remote tank. Oil is fed under high pressure to the crank's two main bearings and rod journals along with other components through internal oil galleys and controlled by an 80-psi bypass. A horizontal oil scraper chamber is built into the rear of the crankcase. During the pistons' downward stroke, oil collected in the crankshaft cavity is first forced into a scraper chamber, then through a one-way reed valve, and finally into the cam case sump for scavenging by the gerotor pump. A case-mounted reed valve eliminates the need for a traditional rotary breather valve.

The engine's top end is lubricated by oil flowing up through the pushrods and returned to the cam case sump through the large-diameter pushrod tubes. Therefore, the cylinders are not machined with an oil return galley. One large and another small hole in the crankcase near the pushrod tubes provides sufficient space for top-end oil to drain into the cam case and for internal engine air to move freely between the heads and bottom-end areas. To maintain a clean-looking silhouette, no external oil lines are used, and the front-mounted oil filter is fed through internal galleys in the cases.

The heart of the X-Wedge engine is its serpentine belt-driven three-cam design. Three camshafts, two exhausts, and one common intake are actuated by a Gates carbon-fiber cord belt kept in adjustment by an automatic tensioner. The three-cam design offers straighter pushrod angles and shorter pushrods for improved valve timing and higher rpm running. When combined with automotive-styled roller-tipped rockers and roller lifters, the result is an incredibility quiet valvetrain. The three camshafts are supported on the right side by a cam plate and on the left by three needle bearings pressed into the crankcase. When assembled, the cams are enclosed in the cam case along with the gerotor oil pump. The three cams are lubricated by oil while the 30mm-wide toothed timing belt and its three idler gears run dry in an adjacent timing chest.

Hydraulic roller lifters, which are shorter and lighter than earlier V-Twin lifters, are secured by lifter blocks integral to the crankcase. The lifters and lifter blocks are covered by common front and rear lifter covers. The rotating cam lobes actuate the lifters, which in turn actuate four pushrods. S&S calls this a "free-spin" design in that the valves will not hit each other or the pistons if the belt should break and the cams go out of phase.

The flattop pistons are forged for strength and designed with small slipper-style skirts. Slipper pistons provide minimum skirt area for reduced friction, narrow pin towers for a short and lightweight pin, and judicious lightening where possible. To further reduce friction and scuffing, piston skirts are coated with an anti-friction coating. One benefit of the X-Wedge's 56-degree design is that there is no need for piston-skirt relief to accommodate large bores, resulting in improved piston stabilization, reduced wear, and increased cylinder sealing. For simplicity, a common piston design is used for both the front and rear cylinders.