KR800 – Kawasaki Rotax 2 Stroke Street Bike

KR800 - Kawasaki Rotax 800cc 2 stroke

KR800 - Kawasaki Rotax 800cc 2 stroke

What was I just saying the other day about not seeing very many mix and match frames and engines in custom bikes? Bill Shank thought we might like to see what he put together in his garage, his KR800, a Kawasaki ZZR1200 mated to a Rotax 800cc 2 stroke engine from a 2003 Ski-Doo. He isn't the first to mount a snowmobile engine in a motorcycle, but it's an interesting combo that, with a bit of refinement, could make for quite a bike.

KR800 - Kawasaki Rotax 800cc 2 stroke

KR800 - Kawasaki Rotax 800cc 2 stroke

Bill wanted to build a 2 stroke street bike to run with current sport bikes. He started designing the project 6 years ago, using as many stock and aftermarket parts as possible to keep the costs down. After three years of free nights and weekends, his KR800 was ridden for the first time and he has titled and licensed it as a "specially constructed" vehicle in Pennsylvania.

KR800 - Rotax 800cc 2 stroke engine placement

KR800 - Rotax 800cc 2 stroke engine placement

Specifications:

Rolling chassis: Stock 2003 Kawasaki ZZR1200 w/ 1-1/8”dia 1020 tubing fabricated engine cradle
Engine: 2003 Ski-Doo Rotax 800SDI (2 cyl 799cc reed induction w/pneumatic power (RAVE) valves, fabricated steel slotted engine plate with urethane bushes (vibration isolation)
Induction: (2)Mikuni 44 SBN carbs mounted on owner fabricated manifold, Vforce-3 reed valves
Lubrication: Stock oil injection w/2qt tank
Fuel: 91oct pump gas, 5.2 gal tank w/external press/vac breather, Mikuni 35 lph diaphragm type fuel pump
Ignition: Ignitek programmable 12vdc CDI w/rev limiter and power valve outputs)
Electrical: 12v-360W Alt/reg-rect w/sealed maint free battery, 40A ckt breaker, Painless (7)ckt fused power distribution
Starter: Modified Honda 390 recoil pull start with owner modified engine pulley
Transmission: 2004 “STD” HD 5spd Softail with custom mounting plate, relocated drain, vent and fill points
Primary Drive: 2004 Rivera 1.75” belt drive/ hydraulic actuated Pro Clutch
Exhaust: CPI Racing custom exhaust w/ 2 into 1 manifold, 4.5” ground clearance
Instruments: Dakota Digital Speedo/Tach, engine temp gauge, neutral and power valve indicator lights
Weight: approx. 525 lb dry
Performance: +100 RWHP on dyno, Top speed:150-170mph

KR800 - open primary and engine cradle

KR800 - open primary and engine cradle

As I said above, a few refinements would be nice. A pull starter? OK, it works, but maybe at least a kick start instead. The engine cradle is also among the "it works" pieces but it certainly needs some redesign. The Softail tranny with open primary is an interesting combo in a sportbike, too, however, the thing to remember is the bike runs, it puts out very respectable power (100+ RWHP) and is currently licensed for the street. I would consider this sort of a proof of concept that could be taken much further. It's a neat idea, I respect the work done so far and, perhaps, someone could run with it and add some polish. Interesting.

Comments

  1. says

    The grin inducing ability of a big 2 stroke is impossible to describe if you have never had the pleasure, having grown up on triple GTs and Hs a big smile spread across my face just looking at this little ugly duckling, and hey, its got brakes that GTs and Hs never had and a frame that doesn’t bend when you open the throttle ;-)
    As the author says, some more development and tidying up and that is a fun scraper to annoy your friends.

  2. B50 Jim says

    It’s kind of like a Whizzer all grown up and on steroids. Love the recoil start! It’s just the thing to show this is not an ordinary bike. And when he twists the throttle and smokes (literally) a couple sportbikes, they won’t be laughing. Who cares that it’s ugly? I think that’s part of the entire idea here. True, the engine cradle needs some work; pragmatic doesn’t have to equal sloppy. Still, it’s a pretty neat job of packaging an engine in a bike when the two were never designed to be a package. I’d like to see how anyone else would do it, especially on a budget. But all in all it’s quite a project, especially for those ring-ding lovers out there. Having been around when those first wicked Kawasaki 3-cylinders appeared on the scene, I have always respected the potential of a good 2-stroke.

  3. sprfrkr says

    Kick start an 800cc 2s? Sure you can do it, but the one time it recoils/kicks back your ankle/leg will be hurting/broke.

    • QrazyQat says

      Would it be all that hard to do? Back in 1970 when I had my Kawasaki 500 triple it was absurdly easy to kickstart.

  4. Ken says

    As much as I think t strokes need to be phased out, I do miss the sound and smells of a two stroke while tuning my sled in my garage during the middle of winter. What I see here is a guy who doesn’t have pro fabrication skills but rather a can-do ability and made something happen without a blue-print or having someone else to copy. Backyard Engineering at its finest!

    • biggyfries says

      Finest? This is a hack job–I like the creativity, but this one deserves a little quality fabrication. If it didn’t look like it was cobbled together from junkyard parts I would be far more interested. There are some fine backyard craftsmen–this guy in not one of them.

  5. reenen says

    This is so, so, so much more exciting and interesting than yet another long, low “custom” without seat or suspension. I also love 2-strokes, having had a friend with a 750 GT Water Buffalo and owning a Yammie 175 IT myself.
    Now how about someone joining two 3 cylinder 750′s for a 1500 V6?

  6. mule says

    I can really appreciate this bike and the fact that it runs and functions. Most of it is very simple. However, the devil is in the primary/tranny interface. The CV set-up found on a sled is super wide meaning it turns into a straight line bike or merely a proof of concept. If you want to bolt a tranny on it, it has to be a Sportster type where the cltch and the countershaft are on the same shaft. Otherwise the rear wheel turns backwards. OR…you have to run the engine backawards and have an ignition intended to run the other direction as well…or run the carbs out the front with the motor flipped around.

    The alternative to all that is a geared primary which takes a lot more design and dollars. When I built one of these, I started with a chain primary, went to gears, engineered myself into a corner and decided I’d revisit the whole concept when I had a pile of money to burn.

    Last thing is, this motor has the potential to make 175+ HP. In the current configuration that this bike is tuned to, everything is functioning and thats the first step. I would say he’s installed it in a fairly heavy package. The motor is pretty light, so this has the potential to be built into a 350-375-lb bike. That would make this 100hp at the wheel very exciting!

  7. Thure says

    In my opinion the only valid reasons for making a custom build like this, is that you are gonna make something that is better than what is currently available. I think the Tularis and the Jaybuilt bellytank triple succeded with that. This bike in its present form is not really an improvement on the original donor bike in any way. And there are stock bikes available that are lighter and more powerful with better handling. Of course if this was built out of need and because the owner just happened to have most of the parts laying around, then I would say it has definitely been a success.

    • says

      “Better” is an extremely subjective concept, and spec sheets do not tell the whole story.

      Besides, I think I’d rather have an imperfect bike built with vision and heart than any “better” bike that I simply bought and took home.

    • Paulinator says

      Thure, somethimes you do stuff for fun. F-U-N…as in enjoyment or plea…You don`t get it, do you?

      …Never mind.

  8. says

    Way to go Bill. You thought of it, built it and got it on the road.
    No one, anywhere, has a pull start Shankawatax 800. Just you.
    Most cool.

  9. Mark L. says

    Bill,

    What the hell is wrong with you?

    All that work and you paint it SILVER?!

    You are loosing cred. really fast……

    I love it!

    Mark L.

  10. Lohmann says

    I’ve dreamed of making a bike with the Ski-Doo/Rotax 600 E-Tec engine ever since the introduction of that really clean E-Tec two-stroke.

    Yes, this bike does need refinements and no, it doesn’t have a super chassis as the Tularis or the TSS.
    But the most important thing; Bill got the bike on the road! Let’s see more two-strokes on the roads again, please!

  11. lostinoz says

    Pull start motorcycle, ahhh it reminds me of my first minibike back when i was a kid, back then it felt to me like this thing probably would to me now!
    Putting street plastics on it would make it cleaner (wouldnt have to be a set of ZZR, anything that would fit would work) and a better cradle would make it more “stock” looking, but other than that, I’d ride it as is.
    525 seems a bit heavy for missing plastics, I’m sure it could be slimmed down to the original 520 dry weight even with adding plastics.
    If indeed as mule says, that the bike is capable of 175hp, that would be 15 hp MORE than stock, and an awesome 2 stroke to boot! It definitely would be a “crap your pants ride” at 175hp, and I doubt many bikes or bikers would dare try to keep up with the bikes potential.
    No matter what the nay-sayers actually gripe about, remember this Bill, youre riding an 800cc TWO STROKE that you PULL START that YOU built!

    I do have a question for all those people out there that ride with an open primary though, arent you the least bit nervous about getting something important stuck in there, like toes?

    • mule says

      Actually I was being conservative. Search the web for snowmobile performance stuff and there’s 200-225hp 3 cylinders, close to 200hp twins and more parts than you can imagine. I have a complete drive train from a 620cc sled waiting to be installed in a bike. I’m thinking Kenny Roberts/ TZ/Ski-Doo Miler! I need to ride it at least once. I’m pretty much recovered from the last crash, so it may be time to start thinkin’ about gettin’ it together.

  12. todd says

    Looks like there’s plenty of room to go with a smaller / narrower / stronger / lighter chassis. Maybe an SV650 frame with GSXR suspension would lop off 100 pounds or so and handle better. Still, it probably can out handle anyone that will be riding it the way it is. Improvements are really all “on paper” unless you’re hiring Rossi to take it to its limits.

    Must be a crap load of fun though.

    -todd

  13. B50 Jim says

    One more thing: How ’bout pulling the mufflers and doing a video of it running open chambers? Bet she’d really wail.

  14. spectator says

    Mmm… I guess the most impressive thing is that it was able to pass some kind of emissions test. I like motorcycles which are at least any two of the following
    1. fast 2. efficient 3. comfortable 4. aesthetically pleasing
    I don’t really see this bike hitting any of these targets.
    1. it’s obviously slow, but to the comments of souping up the motor; who is seriously contemplating a 150+ hp parallel twin in a bolt-on chassis? That is asking for certain death. 2. Its an 800cc 2stroke; that can’t be fuel efficient can it? 3. the riding position might not be so bad, but from the note that it needed urethane bushings to isolate vibes, i’m guessing it will still shake the crap out of the rider. 4. Best case scenario is that it sounds kind of cool, because it looks awful.
    Nearly interesting concept with hideous execution; pass. Props on getting a tag for it though.

  15. Egeek says

    This builder has in his own way let it be known the 2 stroke is not dead. If time and money were not an object, replacing the Semi-Direct Injection Engine with the latest Rotax E-TEC Direct Injected Sled Engine or their no longer in production 951cc PWC engine with Orbital Air Assisted Direct Injection would make this bike even more of a technical marvel. The time has come for the Motorcycle manufacturers to seriously entertain Direct Injected 2 strokes as a viable product that IMHO people would want. Imagine a 250cc 2 stroke Direct Injected Motocross bike, man what a rocket sled, light and 4 stroke fuel consumption to boot.

  16. Scotduke says

    Interesting, not the best looking bike out there but I bet it’s fun to ride. I have fond memories of my old two strokes but they never went anything like this. The drivetrain could do with some improvements maybe but that can come with the MK2!

  17. Nicolas says

    If the frame had its original fairings, you’d only see a bit of exhaust popping out, but otherwize it would be a plaisant looking bike, you grumps.

    Awesome build. Way to go !

    • says

      Most of the new bikes aren’t really that pretty with the fairings removed anyway! If this had the lowers on, the sound would be the only give away. If he did away with the 2-1 pipe and went to individual chambers, he ‘d pick up a load of power on top.

  18. Artie says

    I think it is safe to say that it’s the only bike like this in the world and that’s good enough for me!! PREATY COOL!!!!!

  19. Tinman says

    Im sure this Bike is better than 99% of the complainers will ever build. This Guy got an idea and saw it through to a running bike, 3 cheers!! Two strokes will return just as they have in the marine power field. Direct injection makes it easy to meet the EPA regs.

    • todd says

      not to be too nosey but you have some pretty cool pictures on your album. It’ll be great to see your Blast finished too.

      -todd

      • says

        Thanks! The photos are there for everyone to enjoy, so feel free to check out anything I have in my Flickr stream.

        The Blast project is currently being put on the back burner while I work on my Cyclone. I need to keep one bike rideable at a time =)

    • says

      Boy that R-5 is interesting. Kind of a weird combo of styles. I’ve looked at your pictures before and and yes….very cool stuff in your collection!

  20. Bill Shank says

    The KR800 was a “proof of concept” project inspired by Rob Tuluie’s
    “Tularis”. I knew I did not have the resources and engineering talent that
    Tuluie was able to bring to bear on his race bike and so I would need to
    take a more practical approach. The key decision I made towards this end,
    which influenced almost every aspect of the KR800′s design, aesthetics
    and performance, was to use the Kawi ZZR1200′s rolling chassis as is
    without modification wherever possible. Some observations:

    I agree that the KR800′s aesthetics have a lot of room for improvement.
    The inability to use the ZZR’s stock bodywork lead me to go fpr the Naked or
    streetfighter approach which then exposes the frame and engine cradle.
    The cradle was deliberately overbuilt to cope with the parallel twins
    significant vibrations while retaining alignment with the independently
    mounted HD transmission. I originally used a twin headlight set up mounted to the
    forks with no fairing, which in retrospect probably gave the bike more of a street
    fighter look but left the substantial stock wiring harness exposed.

    Using 1/8″ 1020 tubing for the cradle and similar material for the trans
    mount contributed to the bike’s 500+ lb weight. I also needed to use 1/4″
    steel plate and 1020 tubing for the engine mounting plate after several stock
    aluminum ones failed due to fatigue as a result of the stiffer urethane bushings
    needed to prevent excessive movement of the engine as described above.
    Substituting thinner wall 4130 tubing after a detailed stress analysis,
    combined with optimized bushing material, should make a dry weight of 475#
    attainable. I believe a sub 400# bike would require a purpose built frame that
    would eliminate the engine cradle and trans mount. The beefy HD trans and
    belt drive components also contribute to the 525# weight.

    Performance tuning took a back seat during most of the KR800′s
    development while structural design and operability issues were dealt with. The
    decision to revert back to carbs to allow me to more easily tune the engine also
    necessitated designing a new ignition system that was not controlled by the ECU.
    Downdraft
    Mikuni 44 SBN’s were used in place of the normal TM40 flat slides due to
    clearance limitations and required fabricating a manifold and modifying the fuel
    delivery system to work with the SBN’s unique requirements. I had originally
    used twin exhausts when the engine had the stock fuel injection system (Rotax SDI)
    but the pipe dimensions for an engine of this size did not allow enough ground
    clearance for leaning the bike without dragging the pipes. As the stock engine made
    130hp at the crank with a 2 into 1 pipe, I had a pipe custom built to more optimized
    dimensions. There are indeed many hop up parts and mods available to take this
    engine to 150hp and beyond, but dyno time costs and potential reliability issues
    would likely take me in the direction of a later version of this engine (800R) which
    stock produces +150hp w/carbs and a single pipe.

    What’s next? I am machining a new top clamp for the triple tree to allow
    mounting a handlebar for comfort and aesthetics. This will also provide clearance to
    mount the fairing to the fork tubes which I think will improve the KR800′s streetfighter stance. I have a kick start design almost finished which will replace the pull start and allow easier on bike starting. A final dyno session with two stroke guru John Vertucci (VPE) to optimize the carb jetting, ignition timing and document the power delivery is also planned.

    Finally, I would like to sell the KR800 project to another kindred soul who has the energy and resources to take this proof of concept/prototype to the next level or just
    enjoy riding and showing this unique bike to other motorcyclists. If you are interested in acquiring the KR800 , please contact Bill Shank at wgshank@verizon.net

  21. Andre Santerre says

    Do you have any video of this running?
    I’ve had this very idea in mind for a long time for building a drag bike for the 1/4 mile
    but I would like to to use the CVT system from the snowmachine for no shifting on the 1/4.
    Do you have any video of this bike? I’d really like to see and hear it in action.

  22. Douglas Holt says

    This thought has been in my head forever. Here, finally, I see a custom 2-stroke MARINE engine on a motorcycle. OK….why not a 2-stroke outboard powerhead? I mean a V-6, 150-250 hp outboard powerhead? If you can figure a way to bolt up a clutch assembly and transmission to a Rotax motor, why not a 200 hp Mercury powerhead?