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Technical Inc. Big Bore Kit (345cc)

31K views 22 replies 15 participants last post by  Tang 
#1 ·
I know this topic has been beaten to death but I think I actually found something that might work this time!
As you know, our Ninja 300 is basically the same thing as Ninja 250 in Japan, except USA version has longer stroke.

This company called Technical Inc. happen to have a 290cc big bore kit for Ninja 250(JDM Ninja 300) for the price of 43,000 Japanese Yen

http://www.technical-inc.net/products/detail843.html

bore/stroke: 67mm x 41.2mm (JDM Ninja 250 with this kit)
bore/stroke: 62mm x 49.0mm (stock Ninja 300)

So I was thinking we could achieve bore/stroke of 67mm x 49mm, which would make it 345cc.
Do you think it's possible or would there be another problem for this big bore kit?



 
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#4 ·
I would love to do this, but will there need to be any adjustments to fueling?
 
#17 · (Edited)
You could add more stuff to possibly make more power?

Japanese tuner, BEET makes a high cam for Ninja 250(JDM Ninja 300)
Apparently you can still use stock valve spring.
I don't know how much power it would add, also I wonder if you would lose low end power...because I know for cars, if VTEC kicks in at low rpm, it may cause you to lose power. Although Peske makes variable valve cam gear, is that supposed to be like VTEC?

http://www.beet.co.jp/kawasaki/ninja250/index.html
http://www.beet.co.jp/kawasaki/pdf/ninja250_cam_t1.pdf


Penske from Japan makes a few things http://penske.jp/ninya250/ninja250r.html

wide throttle body


wide valve + head kit



light weight variable valve cam gear
 
#13 ·
Not necessarily, think about all the low compression piston kit for Toyota Supra and all the other cars with turbo set up.
You can change the compression without changing bore and stroke. It all depend on the design of piston. So if the piston was designed to compress hard at top dead center, like how some pistons are shaped like bottom of valves to make sure that they're compressing every space of air possible to achieve high compression, you can get a high compression because of this. Whereas top of piston was flat, you will probably end up with low compression.

I'm not good at explaining engineering stuff so I hope I'm making sense..
 
#16 ·
If you don't change the stroke and only make tiny changes to the piston head or keep it relatively the same but increase bore, you will increase the compression ratio as the relative volume at BDC gets a greater increase compared to what you get at TDC. Hence compression ratio increases. The problem is that at the relatively tiny volumes of these engines, the change in volume is actually pretty huge leading to a pretty large relative change in compression ratio. It's designed around the ninja 250 and brings it up a point. I think we did the calculation for this kit or similar last time on the ninja 300 and saw something like a 3 point increase.
 
#15 ·
It would be fun to review it. Maybe they'll give me a discount with an honest review. :) I gotta be able to keep the kit, natch.
 
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