Small Rotary Engines for Motorcycles?

Rotary EngineGot a note the other day with a question about an engine, possibly for use in a motorcycle. The engine was this 1300cc 2 rotor rotary engine made by Rotamax. After looking at the specs it seemed like an interesting option.

Engine size is pretty reasonable, 22.7"-L x 17.4"-W x 17.9"-H, and it weighs 153 pounds. It puts out 170 horsepower and 130 foot pounds of torque which makes it a very capable powerplant. Rotary engines have always had the advantage of low vibration and Mazda has done some nice things with them in cars but their application in motorcycles has been limited.

I haven't followed rotaries very much and I do not have any hands on time so whether they really would work well isn't clear. I never understood why they didn't take off, I heard emissions were a problem and the seals for the rotors would have to be very durable but beyond that, how did they perform? If Mazda gives any indication, they were pretty high performance engines for their size.

Would this work in a motorcycle? I don't see why not, Norton made the John Player Specials back around 1990 and Suzuki made a rotary back in the '70s, did anyone else make one? Whether they did or not, if someone put one of these in a motorcycle, it might make an interesting machine.

Link: RotaMax


  1. kneeslider says

    Didn’t seem to go anywhere, low sales and then stopped, which pretty much is what happened to the Suzuki. Interesting.

  2. hoyt says

    This type of engine tech makes so much sense for applications such as motorcycles.

    Not only are the hp & torque figures impressive but other advantages are compact design & low c of g. Durability should be much higher today, too.

    Wheels, cranks, & sprockets go around and around…[so do flying saucers 😉 ] Why not pistons?….

    Norton won the senior TT race in 1992 with a rotary.

    Also check out….

    the round engine –
    quasi turbine engine –

  3. D. Bailey says

    Since the 1300cc motor weights 153lbs, maybe combining it with a carbon fiber or titanium(wishful thinking) frame will help it save some weight.

  4. todd says

    I can imagine developing a lighter weight, smaller capacity engine would be a better idea. One of the greatest problems with rotarys were their unquenchable thirst for fuel. Having the sort of experience Mazda has with wankels I’m sure the design has come quite far.

    the biggest hurdle is overcoming the “tried and true”. People are used to the four cycle engine, it is highly developed and reasonably efficient. Diesels have this same problem, perception and lack of developed infrastructure. People are worried they won’t be able to find fuel when they need it.

    It doesn’t matter if something is better, the thing you already have has to have some serious shortcomings before you decide to change. Until the 4-stroke engine (and conventional chassis) exhibits major flaws things like diesel and rotary motors and direct injected two-strokes are a flight of fantacy.

  5. chris says

    my family had a 1993 mazda rx-7 (1.3 liter, two rotor, twin turbo charged, 255 hp) that we drove until 90,000 miles with no engine problems before we sold it. It averaged about 17-18 mpg, but when getting 255 hp out of 1.3L, it makes sense that it would burn a bit of fuel. That was the 3rd gen, and by then most of the problems with the seals, as far as my understanding goes, where taken care of. The new renesis rotary engine in the rx-8 has been successfully taken on a few 24 hour endurance tests. Clearly I am biased, but I love the rotary engines. To get 255 HP, a rotary has basically 4 moving parts vs the dozens involved in a V6 with variable valve timing. They are smooth engines that are a lot of fun in the rev department. Naturally aspirated ones leave a bit desired in the low end torque department, but that is why a low weight vehicle like a motorcycle would be perfect! I have had nothing but good experiences with rotaries, and I have to agree with Todd that it is a perception issue.

  6. C. J. Luke, III says

    I haven’t followed the wankel much after Mazda first started using it. It was lack-luster in the beginning and had durability problems. The first raves about the wankel was for possible use as an aircraft engine because they were touting the high reliability of the design with a high hp to weight ratio. That utilization never materialized, and it seems that no one but Mazda has considered the rotary as a viable replacement to the standard internal combustion engine.

  7. hoyt says

    I wouldn’t say diesels are a “flight of fantacy” based on the Thunder Twin’s progress. Diesels are finding their way into every size of auto in Europe.

    In addition, the Round Engine & Quasi turbine claim to be flexible for various fuel sources. (nonetheless, I do agree that people are resistant for various reasons.)

    It would be interesting to hear from the Norton racer…. With the additional weight moving in a circular path, did this make it harder to turn-in? If so, would this make rotaries, round engines, and/or quasi turbine engines most suitable for a longitudinal crank ? Anyone ever ride a rotary that could offer some feedback?

  8. Kevin White says

    I had an 86 RX-7 with a long list of modifications, it was an extraordinarily fun machine with the zoomiest engine note I’ve ever heard in anything. I’d salivate uncontrollably if any of the big four or the European bike companies started developing a Wankel bike.

  9. aaron says

    other than the norton commander standard and jps sport bikes, suzuki re-5, and hercules motorcycles i can only come up with the van veen 1000 and DKW W2000 from memory.

  10. aaron says

    doh. hit submit before i was ready. I was going to say that the dkw was very similar to the hercules, and may have been the same maker with a different badge…

  11. aaron says

    one more thought – It’s 153 lbs without primary and transmission. there would be more weight and bulk after bolting these on. maybe turboing the single rotor version would be a better idea? 😉

  12. M. Baker says

    If you really want a rocketship, get someone to work the bugs out of the Sarich Orbital Engine. The fuel is burnt twice which should help emissions. The conspiracy theory is that Ford bought the rights then chickened out

  13. F. Ben says

    Rotary engines are really simple engines,and rotary cars fun to drive. I have an ’85 RX7 (1.1Litre 12A engine) and the car is a blast to drive;early engines had apex seal problems ,but that was taken care of long time ago.
    The only problem is that most mechanics don’t know how to work on a rotary engine,which means one has to go to the dealers . The engine would be perfect in a bike.

  14. aaron says

    D. Bailey asked what transmission would work….
    you could adapt a bmw boxer or maybe a guzzi tranny if you wanted it mounted inline with the frame, and a harley tranny is available to bolt onto whatever you want. if one had the time, a sportbike transmission and clutch could be fit to a custom housing, but who knows how much time and money that could consume!

  15. D. Bailey says

    I was thinking the same thing. Due to the fact that it is 22″ long, mounting it inline looks to be the best way. Also talk to RotaMax it’s running 10:1 compression, but they said that can cut they own rotors and that low compression rotors are no real problem. So turbocharging would be a nice option. You will needed to pay a NRE fee for the special cut rotors.

  16. hoyt says

    The MYT is a great concept (along the same “lines” as the other circular engines).

    Check out the video from the auto show….

    Rafeal explains the 850 hp figure was for MYT engines being used for tractor trailer applications. Weighing 150 lbs. instead of the current 3000 lb. diesels…..

    An automobile version of the MYT engine would be:

    4.5 inches diameter
    7 inches long
    25 pounds
    250 – 500 hp
    150 mpg

    Now, what would a motorcycle version of this engine be like?

    3 inches wide?
    15 pounds?
    160 hp?

    …which could make performance motorcycles about 250 pounds in total weight

  17. says

    I had a suzuki RE5.. the first model to come to aus
    It was a good motorcycle . Did not like chain drive
    Should have had a bigger RPM counter…may be to 20,000rpm
    I payed $3500 aus new . Three year,s later $1200 new
    I sold mine for $500 and still going strong . Damn i wish i had it now

  18. Robert Weathers says

    A german company produced a rotary powered motorcycle in the 70’s called the Hercules. I don’t remember the displacement, etc. Currently Rotamax is the only company actually shipping these smaller rotary engines out the door. They definitely improved the rotary engine. The emissions are now extremely low, better fuel consumption and lots more power! I am working on a project with Eric Barger of Rotamax, call him if you have any questions.

  19. says

    First, the Wankel is a 4 cycle motor. That is, it is unlike a 2 cycle in using an actual rotor motion to push out the exhaust. Second, part of the first fuel economy problem was due to the use of a Thermal Reactor style of pollution control. Extra fuel was required to keep a fire lit (so to speak), in the reaction chamber. Third, your average mechanic does not have a machine to reface the trochoid chamber, (you can’t just use a berry hone, or boring machine), so freshening up the top end becomes a very specialized job. Standard Mazdas, used for racing, had a nasty habit of walking the drive gear out of the rotor at high rpm. I hope that would be addressed in a motorcycle version.