Suzuki RE5
Encyclopedia
The Suzuki RE5 is a motorcycle
with a Wankel rotary engine
that was manufactured by Suzuki
from 1974 to 1976.
block. This one machine alone took a year to reach experimental status. The company also holds twenty patents in plating, as considerable research went into the composite electro-chemical materials (CEM) which were used to plate the rotor housing. Testing of the running prototypes took two years. The bikes were launched in 1974. Suzuki enlisted astronaut Edgar Mitchell, the sixth man to walk on the moon, to introduce the bike and give it his endorsement. No expense was spared, and about a dozen motorcycle publications were treated to a week-long test ride and instructional session on the motorcycle. Journalists were flown around the US west coast in Cessna Citation
jets to take their turn riding five pre-production bikes. This corporate attitude extended to the warranty. It was superior to other motorcycles of the day and a full engine replacement stipulated for any engine problem within the first 12 months or 12000 miles (19,312.1 km).
Despite having only a single rotor, the RE5 was mechanically complex and was a heavy motorcycle. The rotary engine produced a lot of heat, which required a number of subsystems such as water and oil cooling and modifications to engine components such as the exhaust pipes. Ignition was CDI
but used two sets of ignition points through vacuum and rpm sensors to light the one NGK gold palladium spark plug. There were three separate oil tanks (sump, gearbox and total loss tank) and two oil pumps (one for normal engine lubrication and cooling and one to supply oil specifically for tip seal lubrication). The throttle controlled not only the primary carburetor
butterfly but a second valve in the inlet manifold of the secondary throat (the "port" valve) as well as the oil pump which provided lubrication for the tip seals by mixing oil with fuel. Five cables in total were moved by the throttle twist grip. The carburetor was similar to that from a rotary power unit in a car and was complicated, by motorcycle standards of the day.
The RE5 could also be optioned with a full touring kit. This included a large full fairing and windscreen, two saddlebags, a large rack and top box. The fairing included two lockable "gloveboxes", and all three bags were also key-locked. Suzuki later made available bolt-on exhaust extensions which prevented damage to the underside of the saddle bags by the hot exhaust gases. An optional touring saddle may have been also available.
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. This tubular "can" motif was also used in the tail light, and spherical indicator lights finished off the "rotary" theme. The 1976 "A" model returned to more conventional styling. Suzuki expected its sales teams to promote the model alongside the 1977 model GS750
, but production had already ceased. The UK-based Rotary Owner's Club records the earliest serial number as 10049 and the highest 16291. From this total production, numbers of something more than 6,000 bikes for both models are indicated.
As of 2010, Suzuki's newly opened museum in Japan does not feature an RE5.
) chamber, giving three rotations of the crankshaft
for every 360° of rotor travel. Compression ratio
is 9.4:1. 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 silicone 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.
and five-speed constant mesh transmission
. 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.
. Five separate carburetor circuits. Suzuki chose to use 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 carburetor. An 18 mm throat splits into two small peripheral induction tracts. The primary butterfly is directly controlled by one of the 5 throttle cables, and this primary circuit gives decent low-speed running. A diaphragm controls the secondary carburetor port, and this is activated when a set vacuum is reached in the carburetor circuit. This much larger 32 mm port enters the rotor chamber between and slightly below the two small primary ports. Indirectly involved with carburetion is the unique "Port Valve". This small butterfly valve pivots in the rotor housing inside the secondary port and is directly controlled by another of the throttle cables. Without the port valve, the long induction tract of the secondary port would fill with traces of exhaust gasses whenever the secondary valve was closed. This occurs as the tip of the rotor passes the induction port at the end of the exhaust cycle before beginning the induction cycle. 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, and is best illustrated by Suzuki Service Bulletin Nine. The carburetor also incorporated a fuel pump
which was mechanically actuated from a given throttle opening to enrich the fuel mixture during acceleration.
, partially due to the mass of the rotor. Leaning of the mixture on overrun also contributes to erratic and "lumpy" running. One way to solve the problem is to shut off ignition entirely on overrun, but this leads to excessive contamination of the combustion chamber by unwanted deposits, which can cause the Apex seals to stick. Suzuki opted for a compromise by using two sets of ignition points. One set of points ran on a dual lobe cam for normal operation, firing the rotor every face. The other set ran on a single cam on the same shaft for triggering the spark plug on overrun. The second set (the B points) were triggered by an rpm sensor (the speed relay) and a vacuum switch, which meant that they worked on engine deceleration (high vacuum) and above 1,700 rpm. This system fired the rotor every second face. This kept the combustion chambers relatively clean. It also served to smooth the lumpy feel of the bike as RPMs reduced on overrun and addressed some issues with backfiring. Engine braking is also significantly improved. The B point system was discontinued on the "A". It is believed that the factory also employed mechanics to visit dealerships and disconnect the B points on any "M" (1975) models still in the showrooms. Suzuki toyed with the idea of two plugs like the Mazda's, but as with so much of their engineering on this bike, overthought the application, believing that they would require two plugs of different heat ranges. The idea was dropped, and the bike shipped with a single 18 mm conical seat gold palladium
spark plug
housed in a copper insert in the rotor housing (NGK A9EFV).
Motorcycle
A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...
with a Wankel rotary engine
Wankel engine
The Wankel engine is a type of internal combustion engine using an eccentric rotary design to convert pressure into a rotating motion instead of using reciprocating pistons. Its four-stroke cycle takes place in a space between the inside of an oval-like epitrochoid-shaped housing and a rotor that...
that was manufactured by Suzuki
Suzuki
is a Japanese multinational corporation headquartered in Hamamatsu, Japan that specializes in manufacturing compact automobiles and 4x4 vehicles, a full range of motorcycles, all-terrain vehicles , outboard marine engines, wheelchairs and a variety of other small internal combustion engines...
from 1974 to 1976.
History
The RE5 was touted as the future of motorcycling. Indeed, RE5 section chief Shigeyasu Kamiya of Suzuki Motor Corporation stated that they had considered a rotary-powered motorcycle as early as the mid-1960s. Basic research and development continued to the end of the decade and culminated in the signing of a technical licence with NSU in November 1970. Suzuki was the 20th firm to do so. The company was at the cutting edge of rotary development and engineered in-house dozens of machines for the rotary production process. Of these, ten were particularly special and included the machine to cut the trochoidTrochoid
thumb|290px|right|A [[cycloid]] generated by a rolling circleTrochoid is the word created by Gilles de Roberval for the curve described by a fixed point as a circle rolls along a straight line...
block. This one machine alone took a year to reach experimental status. The company also holds twenty patents in plating, as considerable research went into the composite electro-chemical materials (CEM) which were used to plate the rotor housing. Testing of the running prototypes took two years. The bikes were launched in 1974. Suzuki enlisted astronaut Edgar Mitchell, the sixth man to walk on the moon, to introduce the bike and give it his endorsement. No expense was spared, and about a dozen motorcycle publications were treated to a week-long test ride and instructional session on the motorcycle. Journalists were flown around the US west coast in Cessna Citation
Cessna Citation
The Cessna Citation is a marketing name used by Cessna for its line of business jets. Rather than one particular model of aircraft, the name applies to several "families" of turbofan-powered aircraft that have been produced over the years...
jets to take their turn riding five pre-production bikes. This corporate attitude extended to the warranty. It was superior to other motorcycles of the day and a full engine replacement stipulated for any engine problem within the first 12 months or 12000 miles (19,312.1 km).
Despite having only a single rotor, the RE5 was mechanically complex and was a heavy motorcycle. The rotary engine produced a lot of heat, which required a number of subsystems such as water and oil cooling and modifications to engine components such as the exhaust pipes. Ignition was CDI
Capacitor discharge ignition
Capacitor discharge ignition or thyristor ignition is a type of automotive electronic ignition system which is widely used in outboard motors, motorcycles, lawn mowers, chainsaws, small engines, turbine-powered aircraft, and some cars...
but used two sets of ignition points through vacuum and rpm sensors to light the one NGK gold palladium spark plug. There were three separate oil tanks (sump, gearbox and total loss tank) and two oil pumps (one for normal engine lubrication and cooling and one to supply oil specifically for tip seal lubrication). The throttle controlled not only the primary carburetor
Carburetor
A carburetor , carburettor, or carburetter is a device that blends air and fuel for an internal combustion engine. It is sometimes shortened to carb in North America and the United Kingdom....
butterfly but a second valve in the inlet manifold of the secondary throat (the "port" valve) as well as the oil pump which provided lubrication for the tip seals by mixing oil with fuel. Five cables in total were moved by the throttle twist grip. The carburetor was similar to that from a rotary power unit in a car and was complicated, by motorcycle standards of the day.
The RE5 could also be optioned with a full touring kit. This included a large full fairing and windscreen, two saddlebags, a large rack and top box. The fairing included two lockable "gloveboxes", and all three bags were also key-locked. Suzuki later made available bolt-on exhaust extensions which prevented damage to the underside of the saddle bags by the hot exhaust gases. An optional touring saddle may have been also available.
Suzuki commissioned Italian industrial designer Giorgetto Giugiaro
Giorgetto Giugiaro
Giorgetto Giugiaro is an Italian automobile designer responsible equally for a stable of supercars and several of the most popular everyday vehicles driven today...
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. This tubular "can" motif was also used in the tail light, and spherical indicator lights finished off the "rotary" theme. The 1976 "A" model returned to more conventional styling. Suzuki expected its sales teams to promote the model alongside the 1977 model GS750
Suzuki GS series
The Suzuki GS series is a line of motorcycles featuring air-cooled parallel-twin and Inline four engines with two or four valves per cylinder. The GS-range of models are considered to be examples of Universal Japanese motorcycles. The range of motorcycles in the series had engine displacements...
, but production had already ceased. The UK-based Rotary Owner's Club records the earliest serial number as 10049 and the highest 16291. From this total production, numbers of something more than 6,000 bikes for both models are indicated.
As of 2010, Suzuki's newly opened museum in Japan does not feature an RE5.
Test rider impressions
The RE5 was quite advanced in its steering and overall handling, and numerous motorcycle test riders of the day remarked on this, some claiming it the best-handling bike out of Japan and close to European marks. It also had excellent ground clearance. The complex B point system (explained below) gave smoother running on overrun and gave some engine braking. Suzuki stopped fitting the B points to the 1976 "A" model and allegedly had dealers disconnect the system on remaining "M" models. It was also noted that the bikes sometimes exhibited a dead spot or hesitation during acceleration as the carburetor transitioned from primary to secondary throat. This is due to poor synchronization between the positions of the primary, port and the secondary carburetor throat valves. There is also some evidence linking this to jetting, possibly an excessively lean primary mixture. The bike is less powerful than Suzuki's 750 of the day but its greatest attribute is tremendous torque. The bike is smooth compared to many reciprocating engines of the day but has a grinding vibration around 4,000 rpm which was often remarked upon in road tests. Despite speculation about worn or misadjusted components, it is more likely a feature of the engine harmonics. Average fuel consumption is around 37 mpgimp,) but road tests sometimes achieved results as low as 28.6 mpgimp and as high as 43.3 mpgimp. In the end, and once over its novelty, test riders found that other than its handling, it wasn't superior to more conventional bikes.Specifications
Specifications:- Wheels: Front 3.25 × 19in, Rear 4.00 × 18in.
- Brakes: Front twin 290 mm (11.39 in) discs, single piston floating calipers. Rear 180 mm (7.09 in) drum.
- Displacement: 497 cc (30.3 cu in).
- Compression: 9.4:1.
- Claimed HP: 62 hp @ 6,500RPM
- Claimed Torque: 54.9 ft.lbf @ 3,500RPM
- Carburetion: two stage, two barrel 18–32 mm Mikuni.
- Ignition: CDI (incorporating a points system).
- Fuel: 17 litres (4.5 US gal, 3.74 imp gal) capacity, 85-95 octane.
- Starting system: Electric, kickstart (the latter intended to be offered only as an option).
- Performance: Top Speed (tested): 168 km/h (104.4 mph).
- Standing ¼ mile: 14.02s @ 94.24 mph (42.1 m/s).
- Wheel Base: 1509 mm (59.1 in).
- Weight (curb with half tank of fuel): 255.4 kg (563 lb).
- Weight dry: 230 kg (507 lb).
Technical features
The engine has a single rotor with a capacity of 497 cc. The rotor spins on an eccentric shaft in a peritrochoid (Mazda uses an epitrochoidEpitrochoid
An epitrochoid is a roulette traced by a point attached to a circle of radius r rolling around the outside of a fixed circle of radius R, where the point is a distance d from the center of the exterior circle....
) chamber, giving three rotations of the crankshaft
Crankshaft
The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...
for every 360° of rotor travel. Compression ratio
Compression ratio
The 'compression ratio' of an internal-combustion engine or external combustion engine is a value that represents the ratio of the volume of its combustion chamber from its largest capacity to its smallest capacity...
is 9.4:1. 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
Ferroalloy
Ferroalloy refers to various alloys of iron with a high proportion of one or more other element, manganese or silicon for example. It is used in the production of steels and alloys as a raw material.The main ferroalloys are:*FeAl – ferroaluminum...
and titanium carbide
Titanium carbide
Titanium carbide, TiC, is an extremely hard refractory ceramic material, similar to tungsten carbide.It is commercially used in tool bits. It has the appearance of black powder with NaCl-type face centered cubic crystal structure...
. The surface of the trochoid chamber which the apex seals rubbed along was coated with a CEM (composite electrochemical material) consisting of nickel silicone 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 clutchClutch
A clutch is a mechanical device which provides for the transmission of power from one component to another...
and five-speed constant mesh transmission
Transmission (mechanics)
A machine consists of a power source and a power transmission system, which provides controlled application of the power. Merriam-Webster defines transmission as: an assembly of parts including the speed-changing gears and the propeller shaft by which the power is transmitted from an engine to a...
. 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.
Carburetion
Two stage MikuniMikuni
is a leading Japanese carburettor manufacturing company that was founded in 1923 and incorporated in 1948. Their business activities are centred on carburettors, fuel injectors and other automobile related equipment...
. Five separate carburetor circuits. Suzuki chose to use 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 carburetor. An 18 mm throat splits into two small peripheral induction tracts. The primary butterfly is directly controlled by one of the 5 throttle cables, and this primary circuit gives decent low-speed running. A diaphragm controls the secondary carburetor port, and this is activated when a set vacuum is reached in the carburetor circuit. This much larger 32 mm port enters the rotor chamber between and slightly below the two small primary ports. Indirectly involved with carburetion is the unique "Port Valve". This small butterfly valve pivots in the rotor housing inside the secondary port and is directly controlled by another of the throttle cables. Without the port valve, the long induction tract of the secondary port would fill with traces of exhaust gasses whenever the secondary valve was closed. This occurs as the tip of the rotor passes the induction port at the end of the exhaust cycle before beginning the induction cycle. 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, and is best illustrated by Suzuki Service Bulletin Nine. The carburetor also incorporated a fuel pump
Fuel pump
A fuel pump is a frequently essential component on a car or other internal combustion engined device. Many engines do not require any fuel pump at all, requiring only gravity to feed fuel from the fuel tank through a line or hose to the engine...
which was mechanically actuated from a given throttle opening to enrich the fuel mixture during acceleration.
Ignition
CDI triggered by two sets of points. A basic problem with the rotary engine design is a lack of engine brakingEngine braking
Engine braking is where the retarding forces within an engine are used to slow a vehicle down, as opposed to using an external braking mechanism, for example friction brakes or magnetic brakes....
, partially due to the mass of the rotor. Leaning of the mixture on overrun also contributes to erratic and "lumpy" running. One way to solve the problem is to shut off ignition entirely on overrun, but this leads to excessive contamination of the combustion chamber by unwanted deposits, which can cause the Apex seals to stick. Suzuki opted for a compromise by using two sets of ignition points. One set of points ran on a dual lobe cam for normal operation, firing the rotor every face. The other set ran on a single cam on the same shaft for triggering the spark plug on overrun. The second set (the B points) were triggered by an rpm sensor (the speed relay) and a vacuum switch, which meant that they worked on engine deceleration (high vacuum) and above 1,700 rpm. This system fired the rotor every second face. This kept the combustion chambers relatively clean. It also served to smooth the lumpy feel of the bike as RPMs reduced on overrun and addressed some issues with backfiring. Engine braking is also significantly improved. The B point system was discontinued on the "A". It is believed that the factory also employed mechanics to visit dealerships and disconnect the B points on any "M" (1975) models still in the showrooms. Suzuki toyed with the idea of two plugs like the Mazda's, but as with so much of their engineering on this bike, overthought the application, believing that they would require two plugs of different heat ranges. The idea was dropped, and the bike shipped with a single 18 mm conical seat gold palladium
Palladium
Palladium is a chemical element with the chemical symbol Pd and an atomic number of 46. It is a rare and lustrous silvery-white metal discovered in 1803 by William Hyde Wollaston. He named it after the asteroid Pallas, which was itself named after the epithet of the Greek goddess Athena, acquired...
spark plug
Spark plug
A spark plug is an electrical device that fits into the cylinder head of some internal combustion engines and ignites compressed fuels such as aerosol, gasoline, ethanol, and liquefied petroleum gas by means of an electric spark.Spark plugs have an insulated central electrode which is connected by...
housed in a copper insert in the rotor housing (NGK A9EFV).