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greg737 · October 6th, 2018, 12:10 PM

I just finished (in the summertime of this year) a pretty big effort to re-install the OEM airbox on my '05 EX250 Fuel Injection project bike.

Way back in 2009-2010 when I first modified the bike with fuel injection I took the easy way with regard to "packaging" all the necessary components (both the remaining original items + all the new FI components). There's just not a lot of room inside the EX250's frame and getting rid of the OEM airbox was an easy/quick way to get a lot of room to position things that weren't there before, like the FI fuel pump.

During the "pod filter years" (Fuel Injected + pod filters) I felt like the bike performed about as well as it had before modifications with one exception, the pod filter solution just didn't feel as good as the OEM airbox in the 8,000 to 12,000 RPM range where (I believe) the volume of the OEM airbox was specifically design-targeted by the Kawasaki engine guys to achieve a resonant frequency.

If you're one of those EX250 riders who regularly take the engine up to the 12,500-ish range you'll know what I'm talking about.

I came to believe that the pod filters might have better performance through the legendary EX250 "flat spot" in the 5,000 to 7,000 RPM range. My guess is that's the weakest part in the OEM airbox performance. You can never "have it all" so the Kawasaki engineers probably had to accept this situation if they were going to give the OEM airbox its 8,000 to 12,000 sweet spot.

October 6th, 2018, 12:10 PM	#6
greg737 - Name: - Location: - Join Date: May 2009 Motorcycle(s): - Posts: A lot.	I just finished (in the summertime of this year) a pretty big effort to re-install the OEM airbox on my '05 EX250 Fuel Injection project bike. Way back in 2009-2010 when I first modified the bike with fuel injection I took the easy way with regard to "packaging" all the necessary components (both the remaining original items + all the new FI components). There's just not a lot of room inside the EX250's frame and getting rid of the OEM airbox was an easy/quick way to get a lot of room to position things that weren't there before, like the FI fuel pump. During the "pod filter years" (Fuel Injected + pod filters) I felt like the bike performed about as well as it had before modifications with one exception, the pod filter solution just didn't feel as good as the OEM airbox in the 8,000 to 12,000 RPM range where (I believe) the volume of the OEM airbox was specifically design-targeted by the Kawasaki engine guys to achieve a resonant frequency. If you're one of those EX250 riders who regularly take the engine up to the 12,500-ish range you'll know what I'm talking about. I came to believe that the pod filters might have better performance through the legendary EX250 "flat spot" in the 5,000 to 7,000 RPM range. My guess is that's the weakest part in the OEM airbox performance. You can never "have it all" so the Kawasaki engineers probably had to accept this situation if they were going to give the OEM airbox its 8,000 to 12,000 sweet spot.