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The Kneeslider

Doers Builders and Positive People

Rotohak – 325hp Twin Turbo Rotary Engine Sidecar

By Paul Crowe

Rotohak - 325hp twin turbo rotary powered sidecar

What it looks like is a nicely done BMW sidecar rig, what it is, is a beautifully crafted, 325 horsepower twin turbo rotary engine powered sleeper, ready to embarrass the unwary. Of course the wheelie bar might give you a hint. Rotohak, the creation of builder Bob Pelikan, is subtle and deceptive, that valve cover jutting through the fairing is a fake.

Rotohak began way back in 1993, when Bob put it together with a normally aspirated Mazda RX7 engine which powered both the sidecar wheel and rear motorcycle wheel through a VW automatic transmission. It looked like a BMW K100 and sidecar, only a close inspection revealed the secret. Bob rode the rig for several years and in 1998, sold it with the agreement he would have right of first refusal if the new owner decided to sell.

In 2001, he got his chance and Rotohak was back in Bob’s garage. He figured it was time to freshen things up a bit and he found a sequential twin turbo intercooled Mazda Cosmo engine at a local Japanese engine importer. This Japanese market only engine puts out 325 horsepower, the Cosmo is sort of a Japanese musclecar. (Bob’s website gives 2 different hp numbers, I chose the lower one but who knows?)

Bob bought a lot of R1150RT body parts which he grafted to the old K100 and fitted a 16 gallon marine gas tank where the engine would normally be and hooked it up to the normal filler cap. The rotary engine sits in the sidecar trunk leaving room for a passenger, too. A lot of fiberglass work, copious amounts of aluminum polishing and a seat from Corbin complete the Rotohak. Except for the hefty muffler, a somewhat different exhaust note and telltale wheelie bar, you might never suspect.

Projects like this are cool. Great performance, good looks and civilized manners, … until you twist the throttle hard. Neat!

Thanks for the tip, Ted!

More photos below:

Rotohak - 325hp twin turbo rotary powered sidecar

Rotohak - 325hp twin turbo rotary powered sidecar

Rotohak - 325hp twin turbo rotary powered sidecar

Rotohak - before final paint and finish, inner works exposed
This in progress photo gives a better idea of where it all fits

Link: Rotohak

Related: Mazda Rotary Powered Motorcycle

Posted on February 12, 2008 Filed Under: Motorcycle Builders, Three Wheel Vehicles


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Comments

  1. taxman says

    February 12, 2008 at 8:18 am

    but does it lean?

    seriously though. it’s pretty cool.

  2. Space Weasel says

    February 12, 2008 at 9:59 am

    I want video! Preferably w/ wheelies and burnouts next to a surprised viper…

  3. Nicolas says

    February 12, 2008 at 10:09 am

    Nice engineering/workmanship … but starting from the initial K100, it’s now just a RX7 with one wheel missing … ? 😉

  4. Lost in oz says

    February 12, 2008 at 11:08 am

    Well, people used to put the 440 magnum into aspens and the 460 into a maverick, in the bike world it was never considered weird to put a gsxr 1000 into a 600 body or in the import world a jdm motor into a civic. Why not combine it all into a side car rig? Jap HP car motor into a bike frame and still retain an almost stock look.
    The bigger question would be, ok whats left? How long will it be before we see a propane fed turbo diesel 6.8L motor in a honda goldwing frame? Not only can it deafen the neighbors, it can pull down a house and drag it down the road all with the wind in your face!

  5. pghcyclist says

    February 12, 2008 at 12:08 pm

    Wow thats ugly. Ugly like a bulldog or a top fuel dragster. Ugly like a prize fighter. I like it. Thanks for sharing. Great work. Im a little confused though. The rear wheel is powered by the BMW and the Wankle; while the sidecar is just powered by the Mazda? I like the little wheelie bar one the back too nice touch.

  6. kneeslider says

    February 12, 2008 at 12:25 pm

    pghcyclist, there’s no BMW engine in there, it’s all Mazda. What looks like BMW engine sticking out of the fairing is just a cover.

  7. Chris says

    February 12, 2008 at 12:27 pm

    pghcyclist: I believe, if I’m reading that right, there is no BMW engine in it any more, just a valve cover that makes it look like there is.

    This thing is pretty funny, in an embarrass-the-dbag-in-a-musclecar way. It’s not exactly sexy, but it’s a pretty cool idea.

  8. guitargeek says

    February 12, 2008 at 12:59 pm

    (boggles)

  9. Mayakovski says

    February 12, 2008 at 1:18 pm

    Dang!

  10. Mark says

    February 12, 2008 at 1:21 pm

    I can’t tell where the water hoses are going?
    Where’s the radiator?

  11. kneeslider says

    February 12, 2008 at 1:43 pm

    Mark, the frame rails are used as coolant passages routing it to a radiator in the front of the sidecar where it lies down with electric cooling fans to move the air. I added a photo to show the layout a little better.

  12. Space Weasel says

    February 12, 2008 at 3:08 pm

    No mention so far of the trick single sided front end. And that last picture makes me think that passengers are out of luck…

  13. kim scholer says

    February 12, 2008 at 3:21 pm

    What is the weight/bhp ratio of this gem?

  14. Tinker says

    February 12, 2008 at 3:30 pm

    The front tire should also be considered as a clue that there is something odd about this Mazda Motorcycle. I suspect passengers can sit OVER the engine, just like the Smart. Does it get hot in the sidecar? Maybe melting plastic hot?

  15. todd says

    February 12, 2008 at 3:43 pm

    If you look at the pictures you can see the engine is in the rear of the side car. Two passengers can sit in front of the engine, comfortable or not.

    What I want to figure out is how the bike’s rear wheel is powered by the VW transaxel (hopefully not an AutoStick from a ’68 bug…). There must be a couple sprockets and length of chain between the two.

    It looks like the balance is just right with a majority of the weight centered between the two rear wheels. I imagine it wanting to push the front tire around when trying to steer just about any time you aren’t slowing down hard enough to load the front tire enough for traction.

    -todd

  16. pghcyclist says

    February 12, 2008 at 5:21 pm

    Whoops look like missed that first line. Thanks guys. I wonder what you could do with space where the bmw engine used to be.

  17. pghcyclist says

    February 12, 2008 at 5:22 pm

    So this thing actually seems more like a car with a “side bike” cool!

  18. Hammerspur says

    February 12, 2008 at 6:42 pm

    pghcyclist Says:
    February 12th, 2008 at 5:21 pm
    Whoops look like missed that first line. Thanks guys. I wonder what you could do with space where the bmw engine used to be.
    —————–
    THAT’s where the passenger rides!

  19. Sean says

    February 12, 2008 at 7:06 pm

    Now add nitrous.

  20. MadScience says

    February 12, 2008 at 10:19 pm

    Hold up…

    I don’t see any forks on either side of the front wheel, and you can see some wierd suspension set-up off to the side.

    I don’t see a rear swing-arm either, which makes sense with the VW tranny.

    I don’t think there is any motorcycle in it, just the body pieces used to make its disguise.

  21. Bob Pelikan says

    February 12, 2008 at 11:55 pm

    I’ll jump in here to answer a couple of questions as the guy that built this thing. 1. The space normally occupied by the BMW engine is a 14 gallon fuel cell. 2. The passenger sits in front of the engine and to the right side of the transmission. Their left arm rest is over the starter. 3. The MC drive wheel is 16 inches in front of the side car wheel and is driven by a 4″ wide cog belt. 4. The transmission is a VW transporter automatic and the engine and tranny are offset about 15 degrees from the center line of the bike so the transmission clears my wifes but. I used CV joints to transfer the power. The sidecar wheel is driven directly from the right side of the tranny.
    I’ll be happy to answer any other questions. My web site rotohak.com has more info too.
    Thanks for your interest.
    Bob

  22. voodoo-chile says

    February 13, 2008 at 12:29 am

    Did you have to do any mods to get that tranny to support over 300 HP…it was originally designed to be driven by well under 100 if I’m not mistaken. I too would like to see video…I’ll bet that thing is a torque-monster!

  23. Space Weasel says

    February 13, 2008 at 1:06 pm

    As a side note…can I mention how cool it is that the builders of the bikes featured on kneeslider (Bob Pelikan, Kenny Dreer, etc.) join in on the discussions of their bikes? Sometimes it’s easy to forget that they are enthusiasts just like the rest of us.

    Thanks, Kneeslider.

  24. todd says

    February 13, 2008 at 4:51 pm

    voodoo-chile, those VW trannies are usually bolted up in front of a blown chevy V8 in a sand rail. In stock applications, sure they’re handling only 100 HP but it’s also pushing around a 5,000+ LB camper. I think it’ll be fine in this application.

    The front steering looks pretty typical for an outfit (sidecar rig). Nothing unusaul there to give away the secret.

    -todd

    -todd

  25. Bob Pelikan says

    February 14, 2008 at 12:43 am

    voodoo-chile, as todd said, these trannies are built pretty stout. I did have it beefed up a little by a dune buggy shop but if I get on it in too high a gear at low RPM, it will slip. Got to keep the revs up. As to a video, there is a clip on my website rotohak.com of an interview that was on the speed channel. I’m just talking about the bike so there is no footage of it going down the road. I can tell you though, I’ve surprised a few knee dragging crotch rocketeers along Skyline Road near where I live. The thing will do a wheelie at 50 and corners like a Porsche. It is all I can do to hang on going around a corner. I’ve thought of velcroing my but to the seat to keep from getting flung off.

  26. OTTO MANN says

    February 14, 2008 at 4:46 am

    I LOVE IT.

  27. Spartandude says

    July 11, 2008 at 12:59 pm

    Just a note on trany deaths. Typically the stresses are from torque and not necessarily horse power. A slow moving high torque vehicle will kill a tranny by shearing teeth, smashing bearings and various other high pressure senarios even with a low horsepower number. While a high horsepower low torque engine will be unfriendly to trannys by spinning the components so fast that the centrifugal forces (change your reference frame and then try to tell me its not there) will exceed the strength of the rotating components. More infor than was necessary, probably, but meh…peace.

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