Suzuki RE5

Compared to piston engines, rotary engines are smooth, light, and compact with high power relative to displacement. Although these attributes are highly beneficial to motorcycles, Wankel-engined bikes remain something of a rarity, even though the rotary engine had once been touted as the future of motorcycling. Suzuki's RE5 was one of the very few Wankel-engined motorcycles ever produced. Other manufacturers whose bikes reached production include: DKW, Norton and Van Veen (who used a derivative of the NSU/Audi engines developed for Citroën). Hercules also produced a motorcycle with a Wankel engine, the Hercules W-2000, that was the first rotary-powered motorcycle. All four major Japanese manufacturers had prototypes or plans, but only Suzuki's RE5 went into production. Yamaha showed their twin-rotor RZ-201 machine at the Tokyo Motor Show in 1972, while Kawasaki tested a prototype as, allegedly, did Honda. ==History==

RE5 project chief Shigeyasu Kamiya stated that Suzuki had considered a rotary-powered motorcycle in the mid-1960s. Research and development continued till the end of that decade, leading to the signing of a technical licence with NSU in November 1970, Suzuki enlisted astronaut Edgar Mitchell, to introduce and endorse the bike. This RE5's warranty was unusually comprehensive, with a full engine replacement for any engine problem within the first 12 months or . Despite having only a single rotor, the RE5's engine was mechanically complex and its numerous subsystems made for a heavy motorcycle. Rotary engines produce a lot of heat, and the RE5 had water- and oil-cooling, and double-skinned exhaust pipes. Ignition was CDI, with two sets of ignition points actuated via vacuum and rpm sensors, to light a solitary NGK spark plug. Three oil reservoirs served the sump, gearbox and total loss tank. Separate oil pumps fed (respectively) the main bearings and the inlet tracts (to lubricate tip seals). The throttle controlled both the primary carburetor butterfly and a second valve in the inlet manifold of the secondary throat (the "port" valve), as well as governing oil supply to the combustion chamber. Five cables in total were moved by the throttle twist grip! The carburetor was similar to that in a rotary-powered car, and was far more complicated than for normal motorcycles. The RE5 options included: a full touring kit that included a large full fairing (with lockable "glove boxes") and windscreen, two saddlebags, a large rack and lockable top box. Suzuki commissioned Italian industrial designer Giorgetto Giugiaro for the RE5 styling. The "tin can" instrument cluster encompassed the usual lights and a low-fuel warning light, total loss oil tank light and digital gear indicator. The tubular "can" motif was also used in the tail light, and spherical indicator lights finished off the "rotary" theme. There were two production models of the RE5, the 1975 M model and the 1976 "A" model, which adopted more conventional styling. Many "A" models were converted M models. The main changes for 1976 included a color changes, GT750-style instruments, blinkers, tail lights and headlight housing. The "B" secondary points for overrun were removed on the "A" model, the chain oiler was removed and a sealed drive chain fitted. By the end of the production run, a total of some 6,000 RE5 machines had been produced. Although the RE5 was less powerful than the contemporary Suzuki GT750, the engine had excellent torque, and was generally smooth, but it exhibited "grinding vibration" at around 4,000 rpm. Average fuel consumption was , The complex B-point system (explained below) gave smooth running on overrun and some engine braking. Suzuki stopped fitting the B points to the 1976 "A" model, and had dealers disconnect the system on remaining "M" models. The bikes sometimes exhibited a dead spot or hesitation during acceleration as the carburetor transitioned from primary to secondary throat. This was due to poor synchronization between the positions of the primary, port and the secondary carburetor throat valves. Some evidence links this to jetting, giving an excessively lean primary mixture. ==Reception==

Although the RE5's frame and suspension were conventional, reviewers remarked on its good steering and handling, aided by good ground clearance. Some reviewers even claimed it to be the best-handling Japanese bike, and close to European standards. After the novelty of the RE5's rotary engine had worn off, reviewers found only its handling to be its winning factor over other bikes. In 1985 Cycle World criticised the RE5 as expensive, over-complicated, underpowered, and hideous; and they declared it to be one of "The Ten Worst Motorcycles". ==Differing design approaches==

The Norton Classic was an air-cooled twin-rotor bike developed by David Garside at BSA, with a fundamentally different design approach. Whereas the RE5 was heavy, overcomplicated, expensive to make, and (at 60 bhp) a little short on power, Garside's design was simpler, smoother, lighter and (at 80 bhp) significantly more powerful. ==Specifications==

Specifications: • Wheels: Front 3.25 × 19in, Rear 4.00 × 18in. • Carburation: two-stage, two-barrel 18–32 mm Mikuni. • Fuel: 85–95 octane. • Starting system: Electric, kickstart (the latter intended to be offered only as an option). • Performance: Top Speed (tested): . • Standing ¼ mile: 14.02 s @ . • Wheel Base: . • Weight (curb with half tank of fuel): 255.4 kg (563 lb). • Weight dry: 230 kg (507 lb). Engine geometry: • Generating radius R = 100 mm • Eccentricity e = 14 mm • Equidistance a = 2 mm • Rotor housing width B = 67 mm • Chamber displacement Vk = 497 cm3 • Compression ratio ε = 9.4 ==Technical features==

The engine has a single rotor that spins on an eccentric shaft in a peritrochoid (Mazda uses an epitrochoid) housing. Since the stationary/rotor gears ratio is 2:3, the rotor rotates by 360° every three rotations of the crankshaft. The eccentric shaft runs on plain bearings, which were better than rollers for heat dissipation. Combustion sealing utilised Apex, corner and side seals. At the three rotor apexes, tip sealing was accomplished with a three-piece seal tensioned by a blade spring. Apex seals were made of a special material known as Ferro Tic, which was a combination of sintered ferrous alloy and titanium carbide. The surface of the trochoid chamber which the apex seals rubbed along was coated with a CEM (composite electrochemical material) consisting of nickel silicon carbide. Side sealing used one blade-like seal and spring for each rotor face on each side (six side seals in total). Corner seals and springs finished the isolation of combustion. Blow-by gases are recirculated into the combustion process. The rotor spins backward in relation to the motorcycle. Primary power transfer to the clutch and transmission is by duplex chain. Clutch and gearbox Wet multiplate clutch, and five-speed, constant-mesh, manual. The gearbox is virtually the same as that fitted to Suzuki's GT750 water-cooled triple. RE5 final drive is by 630 chain via a 14-tooth drive sprocket and 43-tooth unit at the rear wheel. Suzuki used peripheral ports for the RE5, as they give better high-speed running but are known to have low-speed issues. This is dealt with by using a two-stage Mikuni carburetor. An 18 mm throat splits into two small peripheral induction tracts. If this was allowed to happen, when the secondary throat finally opened the engine would first swallow an induction charge contaminated with exhaust gasses causing a momentary misfire and felt as a dead spot or hesitation in acceleration. The port valve is therefore effectively timed to remain closed whenever the secondary carburetor throat is closed, isolating the induction tract from exhaust gasses. Carburetor tuning involves adjusting cables controlling the primary butterfly and the port valve, among other things, illustrated by Suzuki Service Bulletin Nine. The carburetor also incorporated a fuel pump which was mechanically actuated at 35 degrees of primary butterfly movement (later changed to 28 degrees) and as such, on a motorcycle, required a specialized exhaust system. Suzuki dealt with the problem by first exhausting into a large, heavily finned manifold which split the single exhaust into two streams. They then built two twin-shelled exhaust pipes which included air cooling ducts. Each muffler contains a stainless steel inner pipe which both reduced noise and horsepower, but the RE5 exhaust note remains distinctive. ==See also==