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Discussion Starter · #1 ·
So, this crazy idea came into my head a while back of trying to squeeze 40hp out of the Ninja using only stock parts and modifying them... We'll see how much I break those rules.... Either way, I got the extra exhaust can set up with the machine shop guy and I started fiddling with the bike.... I got the needles shimmed this time without pinching the diaphragms, and the bike seems to run a little rich with 2 washers... So I got to thinking, and I might be paying (again), for doing that... Why take away gas, when I can add air....

So here's my airbox mod:

First you take off:
1.) Front Fairings
2.) Seat
3.) Tank
4.) Rear fairing/passenger seat/rear cowl
5.) Rear wheel
6.) Rear fender
7.) Exhaust mount/support/passenger peg, and passenger peg on left side
8.) Battery and box
9.) Then you're in a place to get to the airbox.... Just undo the round clamp rings and slide off carbs... I found this out the hard way...

Then, after about 3 hours of dissasembly (I might be slow, but I'm thorough) you can get to this:


Notice the two holes on the right, this where the rubber boots go to connect the airbox with the carbs...

Start cutting:


and cutting:


and cutting:


and cutting, and filing down the "ribs" inside the airbox to make way for my cover:


at this point, I also cut up the rubber boots going between the airbox and carbs:




And then I took the metal screen that was behind the foam filter (picture 1), and started cutting it up. I needed something that was going to keep large debri out of the box, being that it's right above the wheel, and probably experienced some kick up:



Cut and bent out of focus:


Mounted to the airbox with M2-12mm screws and nuts - they fit perfectly between the holes of the screen:




So, right now the bike looks like this:


Then I put it partially back together and tested, and got some alarming results. I thought it was because it was cold, and it still might be, I haven't tested thoroughly enough yet - that will be tomorrow. Maybe you fellas can give it a hear and tell me what you think. The hesitation you hear is right at 8,000rpm... Am I WAY lean now with so much more air capable or entering the airbox?

Kawasaki 250R Aibox modification - www.newninja.com
 

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Discussion Starter · #4 ·
it's looking that way Felix.... The exhaust is the stock exhaust, no mods yet... I'm waiting for the modified can to be welded and such....
 

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Spooph: I tried the same thing, except I just cit a large hole in the side of the air box to pull in more air. RedRider set me straight and told me that the stock air box actually "pushes" air into the engine at low-mid RPM ranges. Your bike isn't running lean, it's just getting muffed up air waves and pressure, and that's causing the bike to run all wonky. Believe me, I added 4 washers to each jet before I posted up and it ran the same no matter what. I added that small piece back to the air box and dropped the washers back to 2, and it ran perfect.
 

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Yep, you got it right Travisty....

Spooph - It can run right with your airbox mod, but you need a jet kit with a different needle. Basically the stock needle was designed for the stock airbox, and the air pressure resonations that it creates. Or you could get fuel injection (breaking your rule EVEN MORE!).

Ohh and thanks for advertising the forum in your video!
 

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dang i wish i had a more mechanical mind. I'm getting better though. i love messing with my bike. hopefully the shimming of my needles goes well.
 

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Great write up! Curious how the swap to fuel injection would go. Probably not cost effective. Not sure why this bike isn't yet either.
 

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I would love to see a dyno pull before and after! I just love to see people wrenching trying to get the best from a bike!
If I might offer a suggestion...when the bike is boging out If you give it a quick choke tug and it goes away you are lacking fuel. If it dies your rich, I'm thinking your lean... Shimming the needle up a little more my just cure this! Try to stay out of that area for a long period of time, a lean condition can destroy a piston pretty quickly..

Good Luck Keep us posted!

Sumo
 

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I'm just waiting to see someone throw the euro version fuel injection onto one of our bikes. It's only a matter of time until they start stacking up in the salvage yards over there.
 

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Discussion Starter · #12 ·
redrider said:
Yep, you got it right Travisty....

Spooph - It can run right with your airbox mod, but you need a jet kit with a different needle. Basically the stock needle was designed for the stock airbox, and the air pressure resonations that it creates. Or you could get fuel injection (breaking your rule EVEN MORE!).

Ohh and thanks for advertising the forum in your video!
Red, you're a freekin' genius! I was riding it around today, and I can just feel the engine begging for more fuel, so come Tuesday I'm gonna go get the next size jet/needle - I might get the dyno jet kit for lots of options at a reasonable price, but I'm gonna shop around first... Eventually the idea is to get a setup that somebody can duplicate without putting out more than $50 and get massive performance gains... I know it's in there, I/we just gotta let it out. And you're welcome.

SUMO said:
I would love to see a dyno pull before and after! I just love to see people wrenching trying to get the best from a bike!

Good Luck Keep us posted!

Sumo
Unfortunately I don't have money enough to do a total of like 8 dyno pulls, so I'm gonna space them out with 2 or 3 mods in between. I know it's not scientific, but hey, I always got a but dyno, and I know exactly how the bike feels.. I have covered quite a distance. So we'll see where it goes... And in like 4 months my buddy's gonna have one, and then we can do a step-by-step analysis of each of these mods perfected.

And yea, fuel injection would be sweet, but I don't have $1000 right now...
 

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Discussion Starter · #14 ·
I was looking at that felix, but it's going to be difficult... To me, the only way to do ram air is to pull it from from the rear fairings and feed it through tubes through the rear fender. I might go that route after the exhaust, headers and heads are done, but I think for now I'm gonna go the Burt Monroe style - wide open on all sides...
 
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This subject of RAM-AIR has always puzzeled me. The vacuum inside the intake port pulls the air thru the carburetor. The fuel is also pulled into the airstream by vacuum too. Carburetors only work with a vacuum. If the air is pushed into the carburetor then it cant do all the things it is designed to. On the other hand, a fuel injection system pushes the fuel into the air stream so therefor if the air is also pushed in ( ram air ) then it still works well. fuel injection uses ram air and supercharging very nicly. Am I looking at this correctly?
Sleepy
 

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Discussion Starter · #16 ·
in part Sleepy. Fuel Injection on an NA (Naturally aspirated) engine works just like a carb... When the piston goes does on the intake stroke it sucks in air, and the injectors squirt enough fuel in for the amount of air sucked in.... So, if you're using injectors or a carb, your still sucking air in instead of pushing it in...

Now, if you use ram air, a turbo or a supercharger you're forcing air in, which means you just need to proportionally increase the amount of fuel you're sending in as well...

Thus, if we can figure out how to make a ram air setup for this bike, we can get more air into the engine at a higher speed, which means if the carbs are jetted for that extra air, it would work just as well as injection...

The one benefit that injection has over carbs is that it matches the fuel to air much more precise at every instance, including air temp, elevation (air densities), etc....

Making sense?
 
G

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spooph said:
Thus, if we can figure out how to make a ram air setup for this bike, we can get more air into the engine at a higher speed, which means if the carbs are jetted for that extra air, it would work just as well as injection...


Making sense?
If you are pushing the air then it has no vacuum to pull on the fuel. the positive pressure would push fuel backwards into the jet and back into the gas tank. What causes the fuel to move forward thru the jets?
 

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Sleepy - I understand your confusion, and what you are saying makes sense. However carbs don't work because of the vacuum of the engine, they work because of the difference in pressure between the inlet of the carb (air filter side) and the outlet of the carb (engine side). This is the venturi effect. So whether it is NA or forced induction there is still a difference in pressure inside the carb, which pulls out the fuel.

Ram air, although better than nothing, doesn't pressurize the incomming air (at least not enough to overcome the vacuum of the engine). So, the carb works like it normally would, it just gets its air easier.

http://en.wikipedia.org/wiki/Venturi_effect

Forced induction like a turbo or superchanrger does overcome the vacuum - which is why it requires a different setup. A turbo'd carb'd engine requires that the same positive pressure going into the carbs is applied to the vent of the carb bowls, so that the fuel isn't pushed out of the jet back into the bowl.
 

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Discussion Starter · #20 ·
UPDATE: Got the jet today, and started farkeling around with settings...

I was totally surprised that when I took out my carbs I found them to have 98 jets... So I went the largest the kit had to offer, up to a 100, and am currently up to setting 4 on the needles, having tested all the way from 1-3... It's late, I'm tired, and the testing will continue tomorrow... Once I get the needle set, it's time to jack with the air/fuel screw a wee bit, and then back to fine tuning the needles.. Once I have it purring nicely I'll be posting a vid... And then onto the exhaust!
 
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