User:Stefan-S//RE5

The Suzuki RE5 was a rotary-engine motorcyclemanufactured by the Suzuki Motor Company 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 1960's. Basic R and D 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 trochoid 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 Ed 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 U.S. west coast in Citation jets to take their turn riding 5 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 12,000 miles.

The Japanese approach seemed to pursue the most advanced engineering and design solution to each technical challenge. The rotary engine produced a lot of heat which required a number of sub systems such as water and oil cooling and modifications to more typical 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 paladium 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). It is speculated that in 1975 many people expected to be able to service their motorcycle themselves and the RE5 simply looked too intimidating.

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.

The bikes styling was specially commissioned by Suzuki to Italian industrial designer Georgetto Giugiaro. The “tin can” instrument cluster encompassed the usual lights but also 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. That this was a suspected component in the bike’s failure to sell may be evidenced by the change to more conventional styling in the 1976 A model. The bike was allegedly a financial disaster for Suzuki. Losses of more than 30,000 USD per bike have been mooted. In the end, it is believed that around 6,300 bikes entered the market. Of these, around 4,000 were M models and the remainder A models. It is believed that 60% of all units sold were delivered in the United States. The model was still expected to be promoted by sales teams alongside the 1977 model GS750 but production had ceased. As of 2010, Suzuki’s newly opened museum in Japan does not feature an RE5. Despite the bike’s uniqueness, this is perhaps the biggest statement as to the impact its release had on the company. The bike is still supported today by Rotary Recycle USA. The company has a large collection of rotary motorcycles generally and specializes in RE5 parts and service.

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 gives 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 miles per imperial gallon (31 mp usg ) but road tests sometimes achieved results as low as 28.6 (23.8 mp usg) and as high as 43.3 mp imperial gallon (36 mp usg). 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 x 19, Rear 4.00 x 18.
 * Brakes: Front twin 290 mm/11.39” discs, single piston floating calipers. Rear 180 mm/7.09” drum.
 * Displacement: 497cc/30.3 ci.
 * Compression: 9.4:1.
 * Claimed HP: 62 hp @ 6,500 (actual tested at the rear wheel 47.9436).
 * Claimed Torque: 54.9 ft lbs @ 3,500 (actual tested 45.0).
 * Carburetion: two stage, two barrel 18-32mm Mikuni.
 * Ignition: CDI (incorporating a points system).
 * Fuel: 17 litres (4.5 usg, 3.74 impg) capacity, 85-95 octane.
 * Starting system: Electric, kickstart (the latter intended to be offered only as an option37 ).
 * Performance: Top Speed (tested): 168 kph/105 mph actual.
 * Standing ¼ mile: 14.02 @ 94.24 mph.
 * Wheel Base: 1509 mm/59.1”.
 * Weight (curb with half tank of fuel): 255.4 kg/563 lb.
 * Weight dry: 230 kg/507 lb.

Engine
Rotor Unit: Single rotor with a capacity of 497cc. The rotor spins on an eccentric shaft in a peritrochoid (Mazda uses an epitrochoid) 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 3 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 (6 side seals in total). Corner seals and springs finished the isolation of combustion. Blowby 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 5 speed constant mesh transmission. Gear box is virtually the same as that fitted to Suzuki’s GT750 watercooled 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 Mikuni. 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 enrichen 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 braking 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 sparkplug 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 rpm’s 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, over thought the application believing that they would require two plugs of different heat ranges. Thankfully, the idea was dropped and the bike shipped with a single 18mm conical seat gold paladium spark plug housed in a copper insert in the rotor housing (NGK A9EFV).

Cooling
The rotary engine places severe thermal stresses on its cases as two sides of rotor are constantly exposed to high ignition and exhaust temperatures while the third side inducts cool fuel/air mixture. To cope with this and probably capitalizing on their previous experience with water cooling, Suzuki opted for a liquid cooled engine using two separate systems. Oil is used to lubricate and cool the internals of the rotor and water cooled the external jacketing. Oil is fed from an engine sump by a trochoid pump at around 100 psi. The oil is then circulated through an oil cooler mounted across the frame and below the radiator. A pressure regulator also acts as a bypass in case of a blockage in the cooler. A centrifugal pump sends coolant around the external rotor jacketing but via an intricate path in an attempt to even out the massive thermal stresses. Liquid enters at the point of highest temperatures (ignition) passing from the right side to the left and then makes a 180° turn returning to the right side passing near the exhaust port. Most of the coolant is then routed to the very large radiator that sits across the frame in front of the bike. Some of the coolant that was not directed to the radiator is now sent around the inlet port and the left side housing. Its passage is once again reversed before flowing to the radiator. The water cooling is thermostatically controlled and a shrouded fan on the right side of the radiator takes care of excessive temperatures switching on at 106°C and cutting when the temperature falls below 100°.

Lubrication
Internally the rotor is cooled and lubricated by engine sump oil and the aforementioned trochoid pump. Engine oil is filtered by an easy accessible car type oil filter on the lower right side of the cases. The filter includes an internal bypass valve in case of blockage. Further lubrication specifically for the tip seals is provided by oil from a tank located under the seat. An engine driven metering pump sends oil from this external tank into the carburetor at a ratio of around 100:1. Metering of the oil quantity is mechanically controlled by cables from the throttle grip. The metering pump also provided lubrication for the final drive chain. A second line is routed from the metering pump and around the bike ending just above the drive chain behind the sprocket cover. This feature was also disconnected on the A models by a simple blanking plug at the metering pump. The gearbox is separated from the engine sump and has its own oil supply. Suzuki marketed its own brand of Rotary oil but also approved at least two other oils for use in its rotary engine. Shell Super 10-20-50 and Castrol GTX were both endorsed lubricants.

Exhaust
Rotary exhaust temperatures are a staggering 927 C 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 is a little shorter than the length of the external shell. The internal pipe ends in a removable stinger drilled with numerous holes and wrapped in a fibreglass-like material. The stinger (or Spark Arrestor as Suzuki calls it) exits the exhaust system at the end of the external shell. At the front of each pipe was a small forward facing grille which allowed cool ambient air to be forced into the pipe by the bike’s forward motion and to travel the length of the exhaust between the internal and external pipes. It then flowed through the holes drilled in the stinger mixing with the hot exhaust gasses before exiting the system. Even so, Suzuki found it prudent to fit heat shields on the outside of the pipe to further protect riders and pillions. The bike's sound is unique among its two and four stroke contemporaries but also quite loud. Early in production (December 1974, Frame #11901), Suzuki reduced the size of the spark arrestor tubes which both reduced noise and horse power but the RE5 exhaust note remains particularly distinctive.