The story behind Suzukis Rotory Twin

[Jantar]

Republished from the RE5 mailing list: By Sam at Rotary Recycle USA

To The Rotary Community:

In answer to the Rotary Twin question, here are my notes on the background history of the RT Program. Though lengthy, it is important information in understanding the thinking and direction of Suzuki at that time. This is very good information for the RE-5 historian, enthusiast, and collector.
Because of the great length of this total story, I will break it down into sections that I will post over a period of a couple of weeks. The following information is presented in a "you are there" format:

PART 1:

The Rotary Twin (RT) Development Program was a serious "turning point" for Suzuki that can't be stressed enough. This decision revolves around one major factor and event that left such an impact on Suzuki that it shook the foundation of the Rotary Program and the company. It changed their strategy, course, and scheduled production of the RE-5.

Suzuki's motorcycle engineering policy has always been "design for today with tomorrow in mind." Thus, there are built-in provisions to accommodate future developments. Looking at an RE-5, certain things just stand out, such as an oversized radiator, large oil cooler, twin points, hefty generator, huge twin ducted air box, big 295mm twin front disk, 3-stage CDI box, and a monster two-barrel carburetor. These were all for today's single rotor, but designed for tomorrow's twin.

By early August 1972 Suzuki was well along into their quiet Rotary project, with 12 single rotor prototype machines going through extensive field and bench testing. At that same time, engineers had a twin-rotor design off the drawing boards and were working closely with a second R&D team to make up two twin Rotary prototypes. However, Suzuki knew that the twin rotor would be the next generation engine in just a few years and already made provisions for the twin. But, the single rotor had first priority in development and funding, and the twin was a second-stage fill in. In the mean time, daily reports on the 12 prototypes showed that the new, improved, single-Rotary engine developed by R&D performed very well. But, still at times, it took some slight tweaking and refining. Suzuki Marketing was pleased with the reports and requested two RX Rotary prototypes and one cut away engine from R&D wanting to feature them as part of their Suzuki display at the upcoming Tokyo Motor Show in October, 1972.

The Tokyo Motor Show is the "granddaddy" of them all. Anyone who is anyone would have been there. This show gives every manufacturer a worldwide platform to display their latest line up of motorcycles for the forthcoming
1973 season. It also gives them an opportunity to tease and wet the appetite of both public and press by showing off prototype and concept machines. Though marketing had a very good idea, their request for two RX prototypes and a twin cut away engine was rejected because Suzuki did not want to tip their Rotary hand yet. Somewhat puzzled and disappointed by the decision from the top, marketing went ahead without the Rotaries. In October 1972, they set up a fabulous display of 42 machines for '73, featuring the GT-750K triple taking center stage. The whole R&D team was at the show and was excited to see what the competition had to offer for '73.
After making three extensive passes around the sprawling show, they returned back to the Suzuki display and compared notes. The conclusion was Suzuki had the best display, a terrific line up of machines, the most people, and more press coverage than anyone else. As far as their Japanese competition went, Honda had nothing special to speak of but a few warmed up '72 models.
Kawasaki had a new triple to show off, but ho-hum. Yamaha, who was just across from the big Suzuki display, had a modest line up of bland looking, so-so machines. The only thing of mention there was a roped-off, covered display with a sign that read "special sneak preview unveiling at 12:00."
No one on the R&D team gave it much thought.

At around 11:45 a band of reporters were noticed gathering around the Yamaha display, which now started to slowly revolve. This seemed interesting enough, so most of the R&D boys made their way over to Yamaha territory where the crowed was beginning to grow. One reporter said that he heard that Yamaha had a new, updated version of their prototype GL-750 4 cylinder, two-stroke, water-cooled, "fuel injection" model ready for production.
Rumors and gossip were abound with all kinds of speculation. At precisely 12:00 the strobe lights went on and fanfare music started to play. This hype instantly attracted a large crowd, as people started pouring down all aisles straight for the Yamaha display. With all eyes affixed to the covered display, two shapely, smiling models came out and slowly walked around the covered rotating display a few times and pointed to some unseen bulges. This increased the mystique another notch and drew the crowd in closer. The strobe lights stopped, and the overhead and side spot lights took over and fully illuminated the covered display. The two models stepped back and clapped their hands loudly. At that moment, all the covers on the display lifted straight up and disappeared into the ceiling rigging...
unveiling... The new Yamaha RZ-201 Twin Rotor Motorcycle! The crowd clapped, cheered, oooh and ahhhd. The bike was a beauty. Camera flashes lit up like a Roman candle. Slowly revolving around, the overhead lights reflected the rich metal flake cinnamon brown-colored tank, accented by twin white stripes, with a matching contoured tan leather seat. The lower lights highlighted the radiator and showed off the triple-plated chrome radiator guards, twin mufflers, side covers, fenders, and wheel rims. The Yamaha Twin Rotary was absolutely outstanding and stole the show!

Amiss a barrage of questions and a sea of reporters, the Yamaha rep stepped up to the podium and explained that the RZ-201 was a water-cooled Rotary with an oil cooler and had a 662cc twin rotary engine that developed 68hp at 6500 rpm, using two Keihin Cu-carbs. They stated that the twin rotors were uniquely positioned above a five-speed, tuned, syncro meshed transmission for better weight distribution, handling, and servicing. The twin rotors were driven by a triple duplex chain and was lubricated by Yamaha's new CCR system (Charge Cool Rotor - the fuel/air mixture from the carburetor is mixed with oil for cooling and lubrication of the twin rotors). The bike comes with dual front disk brakes, which work independently of each other for safety purposes. In the event of failure, one brake does not negate the stopping power of the other. The RZ-201 also comes with another Yamaha first, a hydraulic rear disk brake system. He went on and on and on and revealed that Yamaha had been working on this twin for years. It was considered one of the best kept secrets in the industry. He ended his dissertation by pointing to the RZ-201, stressing it was a fully working and operational twin rotary, that was tried and tested, was scheduled for full production, would be available at all Yamaha dealers by mid February, and that orders were now being taken.

Well... needless to say, the on looking Suzuki R&D team stood there staring, stunned, and dumbfounded. For one look at this rotary, they all knew there was no doubt about it. This sleek-looking Yamaha twin "Roadster" was a real serious threat and was going to give the Suzuki RX5 single rotor a run for its money, if not bury it! It was at least two years ahead in technology.
To add a little insult to injury, Yamaha reps spotted the Suzuki R&D team gawking at the RZ-201 green with envy. They sent the two shapely models over to give them a gift. The first model handed each a press release packet, which contained color photos, a factory spec sheet, boiler plate media coverage copy, promo spots, patches, pencils, pricing sheets, etc.
The second model handed each a cardboard tube that contained a large RZ-201 wall poster, calendar, and special first-day unveiling factory brochure.
And... An RZ-201 order form!

Stay tuned for the Part 2....

[Jantar]

ROTARY TWIN STORY -- PART 2:

After getting over the initial shock, the R&D Team went back to the Suzuki display and talked about the RZ-201. Some of the lingering questions that kept gnawing at them were:

1. This was the best kept secret in the industry.
2. They could not believe it was made at Yamaha, for quiet inside
sources would have tipped them off.
3. The comment "working on it for years" didn't fit. Where? With who?
4. Why did Yamaha bypass the single rotor and go straight to the twin?
5. Suzuki purchased a full MFG license from NSU/Wankel.
6. Honda and Kawasaki purchased an R&D license only (non-MFG).
7. Where and who did the bike testing (bench and track)?
8. How did Yamaha come up with this machine?

The answer to all of these questions is a story in itself for another time.

** Here is the important turning point: **

The following Monday morning after the show a special, top-level executive meeting was held at Suzuki. They were now faced with the cold fact and reality that by mid February the RZ-201 would be on the Yamaha showroom floors first. This translates into a major cut of the early Rotary market and that Yamaha, with its foot first in the door, would capture at least minimum 75 percent market share, thus regulating the Suzuki Rotary as a "Johnny come lately" (catch up). Not only that, but by drawing people into the dealers to see the advanced RZ-201 would, in turn, increase Yamaha's other model sales as well.

Armed with this, Suzuki went into a semi panic. It forced them to kick up their RX program, fast track all Rotary testing, and give priority and funding to R&D for the twin Rotary. They also pushed up production of their new RE-5 by a year and a half. This was done despite loud protests by engineering, R&D, and marketing. They felt that by rushing the project would create problems down the road. Their protest was noted but was overridden.

Between October and early February of 1973, everything was still "fast track." The two R&D teams were working diligently. The first R&D team working on the RX project was still ironing out minor kinks in the single-rotor engine. It attributed some of the problems through outside parts sourcing. The second R&D RT team put together two twin-Rotary engines
(RT-13 #10013 and RT-14 #10014) and were bench testing them. All eyes were looking toward mid February when the RZ-201 would hit the Yamaha showrooms.


February passed, and no RZ-201s were to be seen anywhere. Most everyone figured that they were on their way -- just slow delivery. The first half of March finds that R&D fitted RT-13 Rotary prototype engine into a test bed machine using a slightly modified RX frame. Twin testing continued both on bench with RT-14 and now on the test track with RT-13. Twin information is somewhat sparse at this time. But notes indicate that, though both Rotaries ran, problems still persisted with carburetion that had not been ironed out. RT-13 was running on the test track when the engine blew, due to seized main shaft bearings from lack of oil and an ongoing problem of overheating. RT-13's engine was pulled, and R&D took it apart for inspection. It was never reassembled. The second test model using the
RT-14 engine was put into the RT-13 frame. This was put through extensive and severe testing. Once again, a few problems kept creeping up. In any event, Suzuki was confident in the R&D team and felt it was only a matter of time before the "Twin" was perfected. They sent an encouraging memo to both R&D teams telling them to keep up the good work and that new improvements in sealing, metallurgy, coating, carburetion, etc., were coming in shortly from the expanded NSU/Wankel main information pool. By the end of April, all the new technology improvements were taken from the pool and were adapted into the RX single rotor and the RT twin. This cured many of the problems, but the twin carburetors were still a little tricky at best -- with lingering on again and off again glitches surfacing. The adaptation of a fiber insulator block from GM (General Motors) and thicker gasket material from CW (Curtis
Wright) helped out quite a bit.

On May 1, 1973, Yamaha issued a press statement that the RZ-201 would not be available until mid August due to a minor assembly line teething problem.
Hearing this announcement, both teams were jubilant, for it now bought them three and a half more months time to work on the engine. And now they were basically on an even keel with Yamaha, as this brought them to within three weeks from the next Tokyo Show in September where they could display the next RX-5 single and the RT-Twin models. They could then go toe to toe with the RZ-201. While the two R&D teams were jumping for joy, Suzuki corporate saw the statement as a red flag and did not buy Yahama's story.
They felt there was more to the story than what meets the eye and felt it was more than an assembly line problem. At this point several rumors started to circulate:

1. Yamaha's RZ-201 Twin developed major engine problems, and it was
back to the drawing board.
2. Outside source part suppliers for the RZ-201 were running way behind
schedule.
3. Yamaha really had an assembly line problem and was revamping it for
better production flow.
4. Yamaha was trying to raise funds to manufacture the RZ-201 by taking
pre-production orders (?).

The real "zinger" is:

5. Inside sources claimed that the RZ-201 displayed at the show was a
dummy that did not run and that the high-polished engine and transmission cases were totally empty.

At this point in time, the RZ-201 falls into limbo and disappears. Over the next three and a half months, we find the R&D team still working on the RX single, and the RT-14 twin was still giving them some minor sealing problems, heating problems, carburetor problems, and timing chain and transmission problems due to the high torque. R&D pointed the finger at outside source suppliers due to the "fast tracking" and that their quality control left a lot to be desired.

By late August there was still no sign of RZ-201 activity anywhere. At this point and because of reliable source information that the bike was a dummy, Suzuki corporate discounted the RZ-201 as a false alarm and threat and moved ahead with the major decision to definitely come out with a twin Rotary.
But, for now and in view of the $90 million+ already spent on the Rotary project, all the tooling is geared for a single. They felt the best direction to take at that time was to get the RX-500 out into the motorcycle main stream to try and corner the Rotary market, capture a lion's share, and then offer a big twin, RT-10, 1000cc Road Cruiser as a new second model generation for the '77 season.

In September Suzuki set up another fabulous display at the Tokyo Motor Show and featured three RX-5s: a burgundy, a two-tone firemist blue, and a two-tone metal flake green. The bikes were the hit of the show, and Suzuki followed suit and copied Yamaha's giveaway (cardboard tubes with promotional items in it - wall calendar, factory spec sheet, radio promos, etc.).

** Per the above link, I have placed some photos of some of the items that were in that cardboard tube. **

Yamaha had a nice display of bikes, but no RZ-201 nor any mention of it whatsoever. The bike disappeared. The only other Rotaries at the show
were:

1. Sachs had five pre-mix, air-cooled W-2000 models -- two red tanks
(one with a Sachs name badge on the tank and one with a Hercules name badge on the tank) that featured a single KC27 engine, one yellow tank (with Hercules name badge) that featured a KM24 single with a shaft drive using a BMW transmission. They also had two other W-2000s: a black tank with DKW
badge and a blue tank with a Victoria badge. All these were trade names
used They also displayed an inline, working KM914 "Big Twin" Rotary engine that was going to be offered the following year as an option (see photos posted). The only other thing of note was that Sachs had two scantily clad/risqué models walking around showing off the new W-2000 Rotaries.
However, show officials did not like their attire and politely asked them to change their clothes (see photo).

2. NTV (Nortorn Triumph Villars) had two twin Rotary prototypes on
display. The first used a Sachs KM24 snowmobile engine (all their R&D did was make two snowmobile engines together). The other used a Sachs KM914 industrial engine and did the same. These machines looked used and tired.

To move along with our story, the next year R&D continued to refine the RX engine, now called the RE and the RT Twin. In September 1974, the full production 1975 RE-5M Rotary made its grand debut at the Tokyo Show. Once again, it was an instant show stopper. On display was an RE-5 in firemist red, one in firemist blue, plus and RX-5 burgundy model. Though initial sales and reserve production blocks showed a very promising future for the new RE-5, sales started to fall off sharply by March 1975 after the public and press put it through their own street and track testing and long endurance runs. Problems surfacing with engine seals, first and second gear, spark plug, and carburetion were the main complaints. This led to "quiet recalls" to fix the problems. This fast tracking that R&D engineering and marketing warned about was now starting to catch up.


Stay tuned for Pt 3

[Jantar]

ROTARY TWIN STORY -- PART 3:

Most cycle magazines poked fun at the softball turn signals, rolodex gauges, and coffee can stop light assembly (all of which did not help the sales of the RE-5). Suzuki was aware that the Italian space age design was ahead of its time and was reverting back to a more conventional look. However, since they were loosing serious money on the RE-5M, they opted to give the RE a cosmetic face lift by using nearly everything on the GT-750 shelf that would fit. They would now offer the bike as a 1976 "A" model. With new improvements and corrections to the engine, plus today's styling, they hoped this would turn everything around and boost Rotary sales. Suzuki still felt that the Rotary was going to be the power source for all future motorcycles.
Needless to say, due to financial circumstances, the RT-Twin was put on hold for 1976. But R&D could continue with their twin prototype and experiments.

In April R&D made some engineering advancements and pulled RT-14 #10014 out of the frame (the engine seized due a Mikuni #37 oil pump going bad) and added RT-10 #10050 with rear disk brake assembly in its place. They put it through more testing. It performed smoothly without a hitch and worked above everyone's expectations. This all was due in part to the addition of three new members of the R&D team, who came over from Yamaha and worked directly on the (now canceled) RZ-201 project. They confirmed it and removed all doubt. The RZ-201 at the show was not a "dummy" but a fully operational twin "Rotary Rocket" motorcycle that was scheduled for full production. With them they brought over inside information, notes and hands-on twin Rotary experience to their Suzuki RT program.

NOTE: RT-10 #10050 was a combination of the best of both engines -- the RT and RZ Twins.

There may be a short Pt 4 to follow in the future.

[stanko]

Good read thanks for that Jantar, those sneaky buggers at yamaha sure knew when to call it a day !

[paturoa]

Shit there is just so much stuff out that that we don't know, makes u wonder if there were any others that didn't see the light of day that we will never know about.

[cowpoos]

waiting for part four!!! dum de doo!

[Jantar]

waiting for part four!!! dum de doo!

So am I. The final part hasn't yet been published on the RE5 bulletin yet, but I'll put it here as soon as I se it.

[Motu]

Good read - I remember the Yamaha rotary,the pictures of it looked very flash (at the time),but they never appeared.Yamaha had a couple of flops with their 750 and 500 twins,so just kept on with the XS650.

I wasn't impressed with the Suzuki rotary at all,it was just so over the top it was completely ignorable.

[Jantar]

The final part

The new R&D Team listened to suggestions, tips, and recommendations from riders, mechanics, and dealers regularly, sifting through the many letters and faxes pertaining to the complex, time-consuming, and often antiquated task in servicing the Rotary engine. With this in mind, the new R&D Team built and tested a revolutionary, advanced, state-of-the-art Twin Rotary
(RT-10051) that was modular in design and had enhanced servicing features that meant that one no longer had to take apart the entire engine to replace parts or do repairs. A few of the enhanced service modifications made were an oil sight glass next to the dip stick, and an identical sight glass was also added to the clutch cover so you could monitor the level of the transmission oil.

Next, the big clutch cover got a treatment. The "bulge" on the RH side (185mm - 7-1/2 inches dia.) now had two 6mm allen-head bolts on the face.
By removing the two bolts, the face plate would come off, thus exposing the complete primary drive gear and clutch assembly, allowing easy replacement of clutch plates and disks. Also, the timing chain now had a master link.
A removable distributor assembly was added, with a special screw to the right side that was an alignment provision so you could put a rod through it to align the timing gear perfectly with the alignment mark on the inside of the case. The transmission, though it seemed to be part of the complete unit, was actually separate and could be removed and replaced with a new one within ten minutes. There was eight different modular assembly features on this engine, which in essence made it a total breeze to replace almost any part on it (even by a novice). One of the master features of this engine was taken from Curtis Wright working with General Motors engineers. On the top left and right housing assembly, there were two aluminum caps held on by two 5mm screws. By taking off the caps, which were very similar to the timing inspection caps, revealed a rotor at 12 o'clock. All one had to do to change the main seals was push it out one end and insert the new one.
The was reminiscent to the Schick Injector razor blade (push the old one out and automatically put a new one in its place).

The last Twin R&D made was #10052. This engine was also modular in design.
The only difference was that this was fitted into a shaft drive system. It was bench tested, performed excellent, and was one step away from being mounted into a frame that had mag rims. This Twin engine now had four spark plugs (two for each chamber). This idea was borrowed from Mazda. Then, all of a sudden and out of no where, R&D received an executive notice from the front office that the Rotary project was canceled and should come to an immediate and abrupt halt. Any and all production of the Rotary, including R&D, should cease immediately. Thus ends the Twin Rotary dream. But the technical advancements derived from R&D were not in vain, for many of the ideas and advancements can be found in the GS models.

Epilogue... Though some of the RX and RP prototypes did get away from Suzuki due to one thing or another, one point is assured -- Suzuki kept all the blue prints and prototypes of the Twin Rotor models. They still have them tucked away in their warehouse. Suzuki invested multi millions in their Rotary dream and envisioned it as the power source of the future.
They were dedicated to that ultimate end. Even after the Rotary project ceased, Suzuki was still a firm believer in the Rotary and had hopes and aspirations that it would once again evolve as a power source for future machines.

With the gas prices of today on a daily rise, a second and third look at the Rotary engine is being seriously considered by many companies... It has recently come to our attention that John Deere has been doing some Rotary experimentation and has come up with a new slant -- let the Rotary stay constant at 4,000-4,500 rpm. This would give the best gas efficiency. What they are experimenting with is a hydrostatic transmission that governs the speed. Therefore, you have an engine running at one constant speed and a transmission going through all the gears automatically for you. Very unique and economical. This would answer a multitude of questions and may be the way to go. It's what Felix Wankel originally had in mind.

Rotary Recycle has also shipped out KM914s, KM24s, and KM27s to NASA in Cleveland, who are doing extensive research. Also, we've sent test engines out to Mercury Outboard and Aviation. Honda currently has seven Rotaries in their R&D department running on hydrogen. Avion Corp. is manufacturing Rotaries for the military R&D. Plus, there are other Rotary engine manufacturers making new single and double units that are available on the open market today. So, the Rotary engine is not dead by any means. It is quietly alive and well, and it's only a matter of time before technology, metallurgy, emissions, and gas efficiency push it to the forefront once again.

[Motu]

Interesting about running them at a fixed speed for economy.In the '70's Sachs marketed several sizes of wankle stationary engines,I didn't have a lot to do with them,but remember them.When I was at Hire Pool they tried the smallest one on lawnmowers,they were very powerful....and that was their downfall.Mowers lasted 3 months in the hire fleet,but the wankle mower bodies were being destroyed.What they found was that people were leveling sections with them - they would turn the blade upside down and run it over rotary hoed land to smooth it out.A normal mower didn't have the grunt for that.We pulled the engines and dumped them in a jumbo bin.

Anyway,about the constant speed - I also worked for General Foods who had a huge fleet of freezer trucks,and also RFL,who ran a nation wide freezer fleet.The freezer unit was powered by a 15hp B&S or Kohler engine,very heavy and usualy mounted at the top of the body,although some trailers had them underslung.We had to lift them in and out by hand,and it was almost impossible to do it by yourself,although I did manage a couple of times on late shifts.

There were some Sachs engines tried as an experiment,and I changed one once.Wow - you could lift it with one hand,very light compared to a B&S or Kohler.They were very economical too apparently,they could run from ChCh to Auckland on one tank,unheard of with the old ''popper'' motors.I guess the back up wasn't there otherwise they would of used them more.

[Jantar]

Anyway,about the constant speed - ....

....They were very economical too apparently,they could run from ChCh to Auckland on one tank,unheard of with the old ''popper'' motors....
The twin rotor engine developed by Norton is now produced as the Mid-West aero engine. It is used extensively by the US armed forces in their drone aircraft, and is becoming a comming choice of engine for homebuilt and experimental aircraft. Light weight with constant speed running giving high power and improved fuel consuption.

So why does my RE5 use twice as much fuel as my GS1200?

[Ixion]

Hm, there's a little bird in my head mumblig on about rotaries having long induction tracts and therefore being inefficient under varying vacuum conditions Presumably a constant speed engine doesn't have vacuum variations, - ie you don't even really have a throttle in a "normal" sense. - prolly just some drunken bird woffling on though.

When they first came out I thought rotaries were going to be the way of the future. Never really quite understood where they lost their way.