Airbox question
06-06-2010, 10:23 AM
#1
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Airbox question
Last night I took out my airbox and noticed that the sponges that cover the top left and rear right holes (don't have a clue what to call this) have totally disintegrated. So I tore what was left of the sponges out of each one because I didn't want it sucking into my carbs. I also only have one cap that was on top of the front one (I'm assuming there should be two caps, one on front and one on rear).
So my question is what are these two areas for? I know that there are hoses going to each carb from there, but I don't know what the purpose is or why there are the other little holes under where the sponge used to sit. I think my bike is running ok without the sponges and rubber caps in that area, but not sure since it's been that way since I bought the bike (I have nothing to compare it to). Do I need to get replacement sponges and caps? And what's the purpose of all this crap?
P.S.: I have a K&N filter. I think the BMC filter has caps built into it from the pictures I've seen, so I've been thinking about switching to a BMC filter. Would I have to rejet going from K&N to BMC?
So my question is what are these two areas for? I know that there are hoses going to each carb from there, but I don't know what the purpose is or why there are the other little holes under where the sponge used to sit. I think my bike is running ok without the sponges and rubber caps in that area, but not sure since it's been that way since I bought the bike (I have nothing to compare it to). Do I need to get replacement sponges and caps? And what's the purpose of all this crap?
P.S.: I have a K&N filter. I think the BMC filter has caps built into it from the pictures I've seen, so I've been thinking about switching to a BMC filter. Would I have to rejet going from K&N to BMC?
Last edited by evines; 06-06-2010 at 10:27 AM.
06-06-2010, 11:40 AM
#2
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those are filters for the slides. K&N filters have seperate triangular "plugs" both front and rear that go over them. BMC has them built in. Both filters should have red filter elements from the filter oil. I have not seen a stock filter so I cannot say. I switched to a BMC from K&N when I installed a Factory 1.1 jet kit. My guess is that you do not have to rejet BUT, see how it runs. I have read that many K&Ns tricked their owners into jetting too rich. Mine definately was too rich, runs great now. JB
06-06-2010, 12:25 PM
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those are filters for the slides. K&N filters have seperate triangular "plugs" both front and rear that go over them. BMC has them built in. Both filters should have red filter elements from the filter oil. I have not seen a stock filter so I cannot say. I switched to a BMC from K&N when I installed a Factory 1.1 jet kit. My guess is that you do not have to rejet BUT, see how it runs. I have read that many K&Ns tricked their owners into jetting too rich. Mine definately was too rich, runs great now. JB
So do I need to get replacement filters (sponges) since mine were destroyed or is it OK without it? And do I need to find another plug since I only have one? I would guess that not having the little filters would allow unfiltered air into the carbs, especially since I'm missing the plugs over it.
I'd really like to understand how this works, and my google searches haven't helped so far. I just don't see why the little holes and filters are necessary. It seems redundant since you already have filtered air in the airbox. Why can't I just plug those little holes, remove the rubber plugs that go over the whole thing, and let that tube connected to each one get air from the airbox? Thanks.
Last edited by evines; 06-06-2010 at 12:29 PM.
06-06-2010, 12:31 PM
#4
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Yes, you want those little filters. They are pretty cheap (17254-MBB-000, $1.55 at ronayers.com) and prevent foreign particles from getting to the carb slide diaphragms and the associated small orifices that feed them.
06-06-2010, 12:38 PM
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I just thought about this some more, and if I understand correctly, the slide needs a pressure differential to open, and it gets that differential from the air in the carb vs the ambient air. The reason there are holes in this area is to allow ambient air in, and the filters filter that ambient air coming through the holes (duh). The plugs are over the whole thing because the pressure in the airbox probably isn't the same as ambient air pressure. Am I thinking about this correctly?
Thanks for the replies. I basically knew nothing about bikes before I started reading this forum, and now I feel like I know at least a little bit.
Thanks for the replies. I basically knew nothing about bikes before I started reading this forum, and now I feel like I know at least a little bit.
06-06-2010, 05:10 PM
#7
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I ordered replacement filters (thanks Hawkrider), and I think I'm going to also try the BMC filter, as I've read good things about it and I like the fact that the plugs are built into it.
I'm a little confused as to why my bike is running ok without the plugs. Seems to me the slide wouldn't open without the plugs, or at least wouldn't open normally.
06-06-2010, 05:27 PM
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Nah, it'll run fine without 'em. I had mine fall apart last year and I ran for several months without. Just make sure and get all the little broken bits out so they don't get sucked into the carbs and plug something.
06-07-2010, 12:47 PM
#11
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The BMC filter has the caps attached to the bottom side of the filter, so switching to BMC would solve the rubber cap problem. I'm just wondering if it's necessary since I like my K&N just fine, and would rather not spend money if I don't have to.
06-08-2010, 09:52 AM
#12
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Yes you need those plugs as without them you are letting unfiltered air into the airbox. So even though the slide will function fine, the whole that is left open when there are missing wiill cause a problem.
Try contacting K&N and they might send you a pair of the block offs.
Try contacting K&N and they might send you a pair of the block offs.
06-08-2010, 12:02 PM
#13
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Yes you need those plugs as without them you are letting unfiltered air into the airbox. So even though the slide will function fine, the whole that is left open when there are missing wiill cause a problem.
Try contacting K&N and they might send you a pair of the block offs.
Try contacting K&N and they might send you a pair of the block offs.
I was going to get a BMC filter before this, but they are out of stock stateside right now.
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