Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/625324
2016 MOTUS MST & MST-R FIRST RIDE P86 Over the past four years, while finalizing development of the production model, the Motus partners established a 12,000 square foot factory in the same downtown Birmingham building that once housed the Barber motorcycle collection before it moved to its present purpose built location. Production of the V4 engine has now been trans- ferred in house to the Alabama factory, thus making Motus a true standalone manufacturer. THE BEATING HEART The KMV4 1650cc OHV V4 Baby Block motor power- ing the Motus, with pushrod actuation of the two valves per cylinder, was conceived as one half of a typical Detroit-built V8, duly downsized, and was cre- ated in the Motor City by auto engine R&D specialist Katech Inc. After Motus Motorcycles owners Lee Conn, 43, and Brian Case, 38, founded their company in 2008, they inked a deal with Katech to develop a motor to power the Motown motorcycle they'd decided to create to plug the gap in the marketplace they'd felt existed for an American-built sport tourer. So the liquid-cooled OHV V4 Baby Block 100ci motor powering the Motus is positioned length- ways in the frame like on a Honda ST1300, with the two cylinder blocks set at a 90º angle. Mea- suring 88 x 67.8mm for exactly 1650cc, the cylinders employ Ni- kasil liners, with bolted-up forged steel Carrillo conrods mounted on the three-bearing one-piece crankshaft via plain bearings, each carrying three-ring Mahle forged pistons delivering an 11.5:1 com- pression ratio. There's a 75-de- gree angle between the crank throws, which delivers a unique trademark engine note for the Motus. The single roller-bearing camshaft is mounted in the block between the cylinder vee, Detroit- style, and is chain-driven off the crank, with steel pushrods actuat- ing each cylinder's two stainless steel valves set in at a 24º total included angle—a soup plate-sized 46.5mm inlet and 38mm exhaust— via maintenance-free GM hydraulic lifters and roller-bearing rocker arms. Despite the closed-up crank throws, the twin contra rotating balance shafts previously fitted to the proof of concept prototype motor to smooth out second-order vibration, have been discarded for production with no ill-effects. The Motus runs a closed-loop top spray port injection system with RBW throttle co-developed by Motus with Oklahoma-based Murphy, with a single AC Delco in- jector per cylinder mounted above the quartet of 40mm downdraft throttle bodies. The Gerotor oil pump mounted at the front of the liquid-cooled wet-sump engine is driven off the camshaft, same as the integrally-cast internal water pump, while bolted on to the rear within an aluminum bell housing is the six-speed cassette-type gearbox with chain final drive, driven by a right-angle gear set off the end of the crank, with fifth and sixth gear both overdrives for long-legged mile eating. The transmission employs a specially designed FCC multi-plate oil bath clutch, and the engine and trans- mission together weigh a claimed 225lb/102kg. The separate twin 2-1 stainless steel exhausts are equipped with a three-stage cata- lyst, and connected via a balance pipe under the gearbox. Designed and built right here, the Motus V4 is unlike any other machine in the motorcycle marketplace. You can have any color you want, as long as it's red or white. Maybe a blue would complete the American trifecta?