2-stroke powered ninja 250r?

Discussion in '2 smokers' started by 81cr450, Nov 25, 2012.

  1. 81cr450

    81cr450 Been here awhile

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    I'm sure I'm not the only one on here who's had the thought of a 2-stroke powered ninja 250r.
    What I'm wondering is anybody "seen" any links anywhere of completed build's. Fabbing a whole bike would be beyond me, but a conversion I could manage.
    I'm thinking it couldnt be much different than building an AF bike. Ideally I like the new CBR 250 r honda with a kx500 motor in it, cause the steel frame would be easier to work with & it's gotta be slimmer with a single cylinder motor which would make everything line up better kicker & sprocket wise.
    If I was to use the 2008+ ninja250 I think the banshee motor would be a better pick to fit the twin cylinder frame. I've seen one of the 1st gen 250 ninja's done on youtube but it wasnt very informative & was only a buzz up & down the street
    cr500 builds would even interest me , just trying find more info period.
    As far as a single cylinder & vibes , it really wouldnt be any worse than in a dirtbike would it?
    Thanks for any input
    #1
  2. Tosh Togo

    Tosh Togo Long timer

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    An RZ350 engine would be worth a look. It's about the same size as your EX250 engine is, but makes more power and weighs less. A Banshee engine would work just as well... you'll be making custom pipes anyway. :evil


    [​IMG]
    #2
  3. jar944

    jar944 Been here awhile

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    The 500cc 2t singles vibrate.. a lot. The counter shaft dictates engine placement and dirt bikes are considerably narrower then most street bikes. because of that Getting a functioning kick start seems almost impossible due to the frame width.

    I've thought about a banshee/RZ powered 250 ninja, I even have a banshee motor sitting in my garage waiting to be swapped into something.

    Pipe fitment on the twin is the issue. keeping it inside the faring would require some effort.
    #3
  4. 81cr450

    81cr450 Been here awhile

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    <a href="http://s1267.beta.photobucket.com/user/81cr450/library/" target="_blank"><img src="http://i1267.photobucket.com/albums/jj543/81cr450/2008-kawasaki-ninja250r-ex250j8f-40130-d4.jpg" border="0" alt="Photobucket"/></a>

    <a href="http://s1267.beta.photobucket.com/user/81cr450/library/" target="_blank"><img src="http://i1267.photobucket.com/albums/jj543/81cr450/2008-Kawasaki-Ninja-250R-Motorcycle-Test-Stermer-011.jpg" border="0" alt="Photobucket"/></a>

    Looks like a bit of room for "a" pipe, might could make room for 2 if you put cutouts in fairing kinda like they do to car hoods when a turbo is peeking through.

    My question about a big single could have been better phrased maybe. I've been riding 2t 500's for the last 10+ years the vibes dont bother me , would it be worse or amplified in a street bike. I realize you'd need to gear it so it would be in the smooth spots at cruise RPM but...

    An RZ350 motor would be good but I think you could get a better powervalve set up with something like the T-rex jugs as well as go bigger. No doubt a twin would be the smoothest, the banshee motors where barely bolted into the frame compared to a dirtbike single

    Offset sprockets arent a big deal to shift the motor over to help with a kicker throwing the weight off center much would be a big negative though
    #4
  5. Motorrad

    Motorrad Been here awhile

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    Kawasaki sucks... why would you want one of those.... get a honda...


    haha..



    Okay..

    I always thought one of those with a HOT HOT built 250R atc motor would be fun..
    #5
  6. 81cr450

    81cr450 Been here awhile

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    The reverse kick would actually work quite well & its counter balanced , 6 speed , 90 hp with a Liger jug :drif
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  7. Motorrad

    Motorrad Been here awhile

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    exactly what I was thinking....
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  8. jar944

    jar944 Been here awhile

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    The vibrations may or may not be more, it would depend on the mounting and frame rigidity. I wouldn't think it would be much of a change either way. It's the constant speed vibration that would get annoying.

    For the banshee, a serval / or cheetah powervalve setup (420 to 485cc) would be plenty of motor. Then swap in a RZ transmission and you have enough gearing for the highway.

    Offset sprockets put more load into the counter shaft bearings, I would avoid them.
    #8
  9. Navin

    Navin Long timer

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    I'm trying to build a decent bike out of a 2013 Ninja 300. The engine is the best part of the bike. There are better chassies to swap a 2t into. Search CL for parted out GSXRs. A roller from any 600 SS would be a far better base to start with.
    #9
  10. 2trally

    2trally Adventurer

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    Have you seen the 450 mono gp bikes? I think it would be easier to start with something like a kx500, change the suspension, gearing, subframe and wheels. Then fabricate some fiberglass bodywork for it. You would end up with a lot lighter bike and there wouldn't be as much custom fabrication.

    Okay, maybe there would be more custom fabrication, but I think your less likely to run into a problem that will stop the project cold by changing the suspension and subframe than by changing the engine.
    #10
  11. Andyinhilo

    Andyinhilo Long timer

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    You might try to find one of these :evil:
    [​IMG]
    #11
  12. Motorrad

    Motorrad Been here awhile

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    just go find a RD500 and get it over with.. spend money... and ride..
    #12
  13. High Country Herb

    High Country Herb Adventure Connoiseur

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    Is alignment that big of a deal? I would mount the motor with the sprocket lined up, then make a custom kick starter to fit the area. A simple dog leg bent into a stock kicker should do the trick, right?

    They used to have some cool 125 and 250 2-strokes at Laguna Seca during the MotoGP races.

    [​IMG]
    #13
  14. jar944

    jar944 Been here awhile

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    On a 125/250 yes, that will work. On a 500 the extra outboard leverage WILL break the case.
    #14
  15. 81cr450

    81cr450 Been here awhile

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    Gixxer weight is the hangup 424 lbs w/fuel . compared to near a 100 lbs less with the 250 size bikes

    The offset sprocket does work you just need an additional bearing set up to the outside. Definitley more fab work though. & I have thought that you could poly mount in a cage with no movement available so it just dampens the vibes

    A cheap more modern suspension bike is why I'm not looking at the buy & ride type. I have a real hard time just riding "stock" machines, tinkeritis bad, Thats half the fun putting it together & making it work.

    I do have the KX550, SUMO really would be the easiest & probably the lightest.

    The 250r motor shifted to the sproket side all the way would leave you more room for a pipe on the other side & you could bend the kicker on it as long as you had a decompressor in the head.

    Thanks for the idea's & the cool pics of the sweet old iron Guy's
    . I admit it's a bit of a PIPE dream at the moment, but thinking it through has really brought in some great ideas. More input definitley welcome.

    Horse power wouldnt be as big of structural detriment as weight, I've read on some other forums that it would just trash a bike doubling the horsepower that the factory intended, but you see guys do that & more on Banshee's & other machines with no ill effect & considering you'd be losing weight with a lighter motor wouldnt that be a big positive structurally?
    #15
  16. Navin

    Navin Long timer

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    #16
  17. High Country Herb

    High Country Herb Adventure Connoiseur

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    That would be pretty easy to do on the kick starter shaft. All you would need is an extension with female and male splined ends, and a couple bearings to keep it all aligned. There isn't nearly as much stress on the kicker, so the bearings wouldn't need to be oiled or anything. 2 skateboard wheel bearings would do the trick.
    #17
  18. 81cr450

    81cr450 Been here awhile

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    I like that idea, much better than bending a kicker.

    Probably right as far as it not really being more modern , the 08+ up just have the more common tire sizes than the older 250 ninja bikes
    #18
  19. Sh0nky

    Sh0nky n00b

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    #19
  20. 81cr450

    81cr450 Been here awhile

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    Thanks Sh0nky that is exactly the kind of thing I was looking for. I googlieyed searched for like a half a day but most everthing I ran across was just "oh yeah that'd be cool" & the starters that dont finish. It was great that they listed a weight there too, I'd assumed it'd be a bit lighter for sure
    #20