The 1980-'83 XJ650 Maxim combined an air-cooled, 653 cc DOHC 2 valves per cylinder transverse inline-4 engine and shaft drive. These days, shaft drive is reserved for big bikes, and air-cooled fours have all but disappeared thanks to tightening emissions standards. And unlike the Suzuki GS650 competitor, the Yamaha engine employed a one-piece crankshaft with plain bearings and placed the alternator and starter behind the engine to minimize width. A chain drives the two overhead camshafts, which used shim-and-bucket adjustment. A second chain drives the oil pump located in the crankcase, while a third (Hy-Vo) chain spins the alternator. The power unit is fed by four Hitachi constant velocity carburetors and lit by electronic ignition. Four-into-two headers extracts the waste gases, which exit through two shortened mufflers. With regular maintenance, these engines live on longer than most people would expect. Though the lack of liquid-cooling will affect engine life in the end, it does add to the bike’s simplicity.
Hypoid gears and a shaft turns the rear wheel, with the shaft housing forming the left side swingarm. The shaft drive is lighter and smaller than conventional shafts, and with proper greasing lasts far longer than several chains and sets of sprockets, not to mention the lubing intervals are far longer.