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Discussion Starter #1
I've seen a number of threads addressing the 900's air intake problems and the expensive aftermarket kits available. I have some ideas on this using the stock air intake and making modifications that would increase airflow and would probably be 1/4 the price (or less) of the aftermarket air intakes. Without getting into to much detail at this point (nothing earth shattering but different from other ideas), I was wondering if there was anybody out there that has replaced their stock filter box/cover/element and would consider selling the stock set-up for a reasonable price so I can play with my idea.
 

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Air Breather

Cut the air restricting metal screen off your stock air filter. Your bike and you will like it. It's like adding 200 cc's. to the engine. Throttle response is much better and acceleration is better through all the gears and at high way speeds passing other vehicles. More air happy engine.
 

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Cut the air restricting metal screen off your stock air filter. Your bike and you will like it. It's like adding 200 cc's. to the engine. Throttle response is much better and acceleration is better through all the gears and at high way speeds passing other vehicles. More air happy engine.
Does this mod require an aftermarket FI add on (PCIII, Cobra FI etc)?
 

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Stock air filter

I just did the mod today and don't know if the bike will require a fuel processor or not. I don't notice any signs of it needing one though. If the bike left the factory running rich then my guess is that the added air flow will not overly lean out the bike. I will need to pull the plugs and get a reading to no for sure but as of this moment, the bike just runs allot better. If I find out that the bike needs a fuel processor, I can always replace the air filter with another stock one or maybe even reattach the metal screen to the filter body. Once again as of today the bike shows no signs of running lean.
 

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Besides choking off air flow, what is the purpose of that screen, does it help hold the filter media within the filter frame?
 

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Air filter

I don't have a clue as to the purpose of the screen, it may be to keep noise down for E.P.A. requirements but other than that I couldn't be sure of it's purpose. I originally thought that the purpose might be to keep larger items from entering the throttle body but nothing can get past all the paper media as far as I can tell. The screen does not add any strength to the air filter as far as I can tell. The whole air filter ass'y. is flexible and is only held on to the backing plate by a single screw. The actual air filter itself is held in place by the out air filter cover by the four screws. If anything gets passed the air filter cover, that would be a huge rock or piece of debris that would have to break the outer cover itself. All I know for sure is the bike is getting a lot more air and is running better than before.
 

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Discussion Starter #11
I take it no one has a stock filter/intake they want to sell??
Anyway since I had my intake apart anyway I took off the screen. I drove the bike after removong the screen and didn't notice much of a difference in performance. I didn't think this was the main problem with the air flow restriction. When you look at the whole intake there are several problems that combine to restrict the air flow.
1) The screen is part of the restriction but really I think you want a bigger element with more surface area. The stock element (not taking folded pleats into the calculation, there is only ~20 sq in of surface area. Most of the aftermarket kits double or even triple this surface area.
2) The air has to go through to many turns before it gets to the throttle plates. Air flow at ambient pressure doesn't like to make a bunch of sharp turns. This causes turbulent flow which in turn causes a pressure drop. All this means is less air to cylinder.
3) The fresh air is taken from between the cylinders which is very hot. Hot air is less dense than cool air. That why you may notice a difference in performance on cool evenings. The intake should be faced out away from the engine heat.
Even doing all of these things with an S&S aftermarket air cleaner and aftermarket fuel management system, the 900 only made 3 more hp and ~ 1 ft lb more torque. So just removing the screen would have minimal effect. Go to link below for dyno, click green "view" button to see chart.

http://www.sscycle.com/modules/dyno/index.php?z_catagory=LIKE&x_catagory=4&Submit=Search
 

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The screen does block a lot of air. I couldn't bring mine in our lab to measure flow so I did a seat-of-pants test. Pulled the airbox and left the cover off. Taped up the inlet with a tube sticking out for an air line nozzle. Sat the mess on the bench about 6 inches in front of a 8x11 sheet of mylar with several slits cut in it. Opened up the air and watch the mylar blowing in the breeze. I did this with the OEM filter, OEM w/screen removed, Uni Foam 40 PPI, and Uni Foam 60PPI. This all took less than 45 minutes. I'm now running the Uni Foam 60PPI. My air inlet has also been relocated just beneath the idle screw. I never got around to measuring the temperature difference of relocating air inlet...it's one of the many things on my to-do list for winter. It's boating season and no time for tinkering - only riding.
 

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Here's a question... is the metal screen on the air intake side of the filter, or on the engine side? The reason I ask is, if it's on the engine side, it's probably to protect the engine from sucking in pieces of the filter should it get damp or worn in some way.
 

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Ahh, that will probably keep me from trying out this poor man's mod, then. I'd hate for that paper filter to get damp, deteriorate, and drop chunks of pasty debris into the engine.
 

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I cut out the screen and removed the OEM paper element. I then cut and installed a K&N filter element that I had left over from a mod I did on my Chevy Silverado. It seemed to help some, especially on accelleration....
 

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Ahh, that will probably keep me from trying out this poor man's mod, then. I'd hate for that paper filter to get damp, deteriorate, and drop chunks of pasty debris into the engine.
You misunderstood. The screen is the last thing the air passes through before it gets to the throttle body. Functionally, the screen is on the engine side. Physically, the paper is nearest the engine block.
 

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I cut out the screen and removed the OEM paper element. I then cut and installed a K&N filter element that I had left over from a mod I did on my Chevy Silverado. It seemed to help some, especially on accelleration....
I was thinking along the same lines. Actually I remember the K&N filter for the VN500 I had was about the right shape and size of the paper element area on ours.
 

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Why is stupid K&N still making a filter for the 750, a bike that hasn't been in production for almost 4 years. Or for the 500. But nothing for the 900 which has been around for 4 yrs and ain't going nowhere. Are they just retarded or what? I mean how many 900's are on the road.
 

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Why is stupid K&N still making a filter for the 750, a bike that hasn't been in production for almost 4 years. Or for the 500. But nothing for the 900 which has been around for 4 yrs and ain't going nowhere. Are they just retarded or what? I mean how many 900's are on the road.
I contacted UniFilter and more or less told them the same thing. I mentioned they had filters for a number of other Kawis and said there would be "a ready and appreciative market" in the 900. The guy i contacted agreed and said to give them six months.

Maybe there's hope on the horizon for us?
 
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