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Discussion in 'The Garage' started by indr, Feb 18, 2013.
On a lot of bikes the boot between the airbox and the carb mouth also functions as a velocity stack and has a bell mouth in the airbox.Carbs work better when the air has more speed to the flow.To do a thorough job of correcting jetting you would need either a wide band o2 sensor with gauge on the bike or a day or 2 of dyno time.The only bike I have personal experience with is a 1st gen yamaha fz1.I just put a jet kit in it and followed the instructions in the kit for modding the air box lid.Most of the guys that put pods on the fz1 lost hp and some low speed smoothness.You would probably get better results with opening up the air box lid and running a clean filter but even this might need some jetting correction-only dyno time will tell.Unless the bike was set up rich(unlikely) opening up the air intake will need more fuel-mostly at wot.The dyno usually gives you a a/f ratio graph with when you make a run.Only a dyno will tell you if you are correct.The butt dyno is never correct.
I put pod filters on my fz1 out of necessity due to subframe mods and I think it made it worse. Screams up top but messy down low. Id do stock personally. Plus pods suck to clean
And mine was a matched kit with new velocity stacks and jetting kit from ivans and I followed the instructions to a t.
the days in which you could greatly improve the peformance of your bike in your back yard ("Measure with te Rule, Mark with Chalk, Cut with a Torch") are pretty much over . . . . . your engine, as you know, is a system . . . . the airbox is likely boosting the performance you are getting out of that system, rather than throttling it . . . .
But, it IS possible that one, very specific facet of performance could be improved through such a modification (i.e., power at one, small RPM, range). Enjoy yourself!
Changing the intake restriction (airbox removal, different filters) will dramatically alter jetting.
The original question was abpout fuel economy right? I think you are correct in your assumption that if you rejet to the appropriate mixture for the new volume, your fuel consumption will go down.
However, as others have said, I think you probably would ose some level of efficiency so power loss "could" be an outcome as well. More gas, less power. Awesome!
My FZ1 has that problem and it SUCKS!!! Highways make it worse any cross winds and the jetting goes right to shit. Back roads it doesn't do it, which is just fine by me
When I installed a Factory Pro con. 30 (two large oval BMC airfilters, needles, mains) my '97 Bandit 1200S would stumble every once in awhile depending on wind direction and speed. Rerouting the overflow lines up and out of the airflow eliminated all fueling issues in my case. In addition my mileage went up to 44 to 45 mpg from the Dyno-Junk Stage 1 40 mpg.