CBRWorld.net

Has anyone, or does anyone know someone who has put a 250cc two stroke engine onto say a kawasaki 250? I was wondering how hard it would be to do and what would be necessary for engine modifications. it seems that 250's are hard to come by and would make a fun project.

I assume you mean a ninja 250? which is a parallel twin. and I assume you are refering to a single cylinder with reed style exhaust for the swap. asside from the obvious differences, the ninja is heavier than the frame of the 250 donor. not that it couldnt be done.

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CBR929-jardine race can, down 1, polished frame and swing arm,wheels polished, HELI bars, Sargent seat, Puig racing screen

commuting on a VLX600 shadow for now, 60MPG!!! I punched out the baffles, so it has that V-twin snap and crackle that made H/D so infamous. Except this little scute is rice powered!!lol

and once in a while a 98 gold wing, its a scarey fast 2 wheeled yacht!!

hubbards right. since ud end up w/ an off-road/track only bike either way u do the swap... ud end up w/ a much faster bike turning a 250 dirtbike into a roadracer. i personally think it would also be easier mounting new wheels to a dirtbike and altering the suspension than transplanting an engine into a ninja250 frame. but hey, anything is possible w/ good machineshop and welding skills.

heres a few examples:
http://www.2wf.com/content/view/1829/45/
http://www.cycleworld.com/article.asp?section_id=3&article_id=479

edit: heres the real website i was looking for... www.450moto.com

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Naked 93' F2...... RIP -- 04/12/07
04' 600RR Black - currently stuck between track and street usage
- Brembo Master, Sato's, & Ohlins out back

hey thanks for the websites. i knew about the 450 singles, but i was only asking cause i have an '01 cr 250 and thought it might be cheaper and fun to mount the 250 engine on a ninja 250 to use as a track only bike.

I have both the Ninja 250 with its 4 cycle twin and the KLR 250 with its industrial revolution era single cylinder.
I think it would not be fun on a track with KLR's engine in a ninja.  It has really good low end torque, thats why it is so fun to ride the KLR in the city and the mountains/desert.  But as soon as you get above 5K RPMs it feels like the HP curve is actually going down, no top end power.  Ninja's twin on the other hand doesnt start to come alive until about 6-7K.  So the conversion might be fun if you make the ninja into a street fighter, but nothing high speed.

thats exactly what i knew the problem would be with the two stroke engine. but i was wondering if i could do anything to the engine to linearize the power and torque curve more than what it is now. i was wondering if anyone knew what i would need to do in order to achieve this bc the way it is now, like you said, i wouldn't imagine it being that fun on the track.

I would think that your idea  would work, but you would need much more displacment. Like a honda 400ex or comprable motor tranny combo. And if Im not mistaken they already use a 6 speed tranny, Just not sure how the gearing would affect it since the quads are geared much lower but can still hit around 100mph or so. I would imagine the weight to be a lottle closer to that of a ninja 250though.

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CBR929-jardine race can, down 1, polished frame and swing arm,wheels polished, HELI bars, Sargent seat, Puig racing screen

commuting on a VLX600 shadow for now, 60MPG!!! I punched out the baffles, so it has that V-twin snap and crackle that made H/D so infamous. Except this little scute is rice powered!!lol

and once in a while a 98 gold wing, its a scarey fast 2 wheeled yacht!!