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Discussion Starter #1
Having massacred the existing airbox on my 904 Bonnie and fitted a pair of K&N filters, it seems I am having a little more difficulty establishing a reasonable fuel/air mix than I expected.
:???:
Lacking a pair of 150 main jets and being forced to rely on my 130's in the meantime, my solution has been to temporarily reduce the airflow with strips of duct tape and an old pair of socks (black, of course) until I get it dyno-tuned next week. I added tape and folded the socks over a couple of times until the ride "felt right(ish)" and then popped next door where my friendly neighbour was kind enough to measure the CO2 content of the exhaust gasses.
The results were: 1.8 at tick-over, and; 3.0 at 2500 rpm. However, it's all Greek/Serbo-Croat to me and I don't really know enough about whether this means I'm running lean or rich.
I have to travel a hundred miles or so southwards to get it dyno-tuned and I don't want to be way too lean or rich on the way down, so can anyone out there tell me if I'm in the right ball park or not?



Heath Robinson is alive and well, it seems! :razz:
Cheers.

[ This message was edited by: keef on 2006-04-10 12:39 ]
 

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what people often forget is that the airbox improves air supply to the engine.
This is because the engine only sucks for 1/4 of teh time putting a peak load on teh capabilities of the filter, an airbox acts as a reservoir of air thus allowing more time for teh air to flow, thus improving air flow. so the bigger you airbox the better the flow for any given filter, up to the point where there is no restriction.
 

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Discussion Starter #4
Panda,
A fair point, I'm sure, though I'd guess that it would be more so for the 970 or 865cc with standard pipes than the 904cc with free flowing pipes. As I've increased the capacity of the cylinders and reduced the resistance of the exhaust, I gather that I've increased the demand for airflow beyond the capacity of the standard airbox to supply it.
Either way, as a result of my butchery, I've crossed that Rubicon.

On 2006-04-10 15:17 Dardoonk wrote:
With the Freak; the world is your airbox.
Amen - I love it - I'm now a FREAK freak!
:-D
 

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On 2006-04-10 14:39, panda wrote:
what people often forget is that the airbox improves air supply to the engine.
This is because the engine only sucks for 1/4 of teh time putting a peak load on teh capabilities of the filter, an airbox acts as a reservoir of air thus allowing more time for teh air to flow, thus improving air flow. so the bigger you airbox the better the flow for any given filter, up to the point where there is no restriction.
Codswallop!
If this is so how do you explain the increase in HP with K&N filters over stock airbox? In my case just over 8 HP with nothing else changed?
 

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1.8 and 3.0 is ok (3.0 is a little rich). BUT the problem is that you only know it's ok at idle and at 2500 with no load on the engine. Not much air needed when not riding...
My guess is that it's better to just used the choke if it feels lean and take it easy until you get some bigger jets, your setup might flood the engine at speed... or it might do nothing.. who knows?
 

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On 2006-04-10 15:42, keef wrote:
Panda,
A fair point, I'm sure, I gather that I've increased the demand for airflow beyond the capacity of the standard airbox to supply it.
Either way, as a result of my butchery, I've crossed that Rubicon.
If possible ( ie if there is room) construct a new airbox with two (or more) filter elements. each one you add doubles the area for airflow without compromising filtering. Not a popular mod, does not look 'cool' but there we are.

dickbender... i doubt the k&N's filter as well as the original filter. I also note from your intro line your bike is not entirely stock :)

[ This message was edited by: panda on 2006-04-11 13:24 ]
 
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