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Discussion Starter · #1 ·
Hi. I have a 1981 Kawasaki 440 LTD that I bought in September of 2009. I replaced a diaphragm in one of the carbs that was cracked and cleaned things up a bit and it runs really well. I would like to move the airbox and air filter so I can put on a solo seat in a lower position. I have spent the last 2 hours reading posts on this forum explaining why pod filters are a bad idea, and that's fine. I'm not looking for more performance, I just want it to run like it does now but with a lower seat.

I have two questions. First, if I build a custom airbox with the same volume as the stock box and even use the stock air filter to maintain stock air flow rates, but make it in a different shape so it can be moved somewhere else, do you think that will work or is the shape of the stock airbox more important than the volume?

Also, there is a tube coming from the top of the engine to the airbox. Seems like some type of reburn/emissions thing. Is that what it is? Can I cap it and not use it? I pulled it off the airbox while the bike was running and the engine died pretty quickly. Maybe the carb on this bike requires the pressure in the airbox created by it. I can plug it into a custom airbox if need be, but I'd rather not use it if that's possible. If someone could explain the function of this setup I would really appreciate it.

I'm sorry to post yet another 440 airbox thread, but I really need to figure this out before I start cutting pieces off the frame off to lower the seat.

I appreciate any help you can give me.
 

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The hose from the top of the engine is the crankcase vent, so NO you can't cap it. Volume on the airbox would be the main thing although I'm not sure what effect making longer boots to connect the carbs to the airbox would have.
 

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There's a lot of thought, engineering, and experimentation in the final airbox design. But that said, most carbs are not too fussy and the bike will run with open mouths to clogger filters. So do your creative best with not much chance of worries about a lousy result.
 

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A lot of thought? By the looks of mine it was designed to fit the space behind the carbs and between the frame rails in front of the battery. I really think space limitations has more influence in the design than any shape or even volume. Room for the filter and the boots is what is important.

Also you cannot run CV carbs open mouth.
 

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Maybe I give the Japanese engineers too much credit. I used to be close to Tier 1 auto suppliers for Honda, and they drove us nuts with details and tight specifications on dimensions.

How come you can't run a CV carb open mouth? It would certainly be bad for dirt and grit, but wouldn't the engine run?
 

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CV carbs use a pressure difference on one side of the diaphragm vs. the other side to lift the slide. Removing the airbox will affect this. I wouldn't say you "can't" run it open mouth but throttle response gets jerky and it will have to be re jetted.
 

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A lot of thought? By the looks of mine it was designed to fit the space behind the carbs and between the frame rails in front of the battery. I really think space limitations has more influence in the design than any shape or even volume. Room for the filter and the boots is what is important.

Also you cannot run CV carbs open mouth.
That is really the engineering that goes into this, yes, the factory airbox is designed to fit in a certain space, but it is also engineered to have a certain volume and air flow pattern as well as meeting noise and/or emmissions requirements. Trying to get all of this in a certain size, within production budgets can sometimes be a real magic act, and one frankly that is hard to improve on, given all rpm ranges, although it is one that is easy to improve upon for a paticular rpm range, with the understanding that the bike will run worse than stock at other rpm ranges. Really depends upon if you want a track bike or a all around, all temp ride.

Perhaps the new airbox can be made in a two part piece and designed to be wider, but lower to keep the volume about the same as stock? That way it could be inserted in thru both sides and take up some of the space under the side covers?

My thoughts - David
 

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Maybe I give the Japanese engineers too much credit. I used to be close to Tier 1 auto suppliers for Honda, and they drove us nuts with details and tight specifications on dimensions.

How come you can't run a CV carb open mouth? It would certainly be bad for dirt and grit, but wouldn't the engine run?
Pull them off your bike and try it.
Sure you could fiddle with it and get it to move along but it would not be worth riding. The air horns that operate the slides are at the top of the entry-way and it takes a ram effect to get them moving air just right to get a smooth power delivery. The boots act as a channel that directs the air over the entire opening but if you eliminate them you get air coming around the sides which will follow path of least resistance. Meaning directly into the throat and the turbelance that you get at the banana shaped slot where the air is directed to operate the slides will be anything but smooth. Which means it will most likely run like crap.
 

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I'll give you my $.02 worth.....based on a lot of experience with these bikes when they were new. If you currently have a good airbox consider yourself lucky, they are getting hard to find. This bike is very fussy about how it runs, if you put the air filter on wrong they run like crap. They are so sensitive that back when they were new Kawasaki sent out a TSB to all their dealers explaining how to properly install the air filter.

Do what you want but to end up with a bike that runs poorly and looks the way you want it seems to me to be a poor tradeoff.
 

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One thing is for sure, it seems to take engineering magic to get these complex airboxes off an onto the bike. Ever hear of a Helmholtz resonator? I studied them for a couple of years about 32 years ago.
 

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Discussion Starter · #11 ·
True enough about getting the stock airbox out. That thing is jammed in there pretty good. Does it just come out or do I have to take some other parts off to get it out?

It seems to be pretty well established that these carbs are quite touchy (I've experienced the ill-fitted airbox situation). Are there any others carbs that you guys know of that will work? A custom intake would be a headache but certainly doable and worth while if I can lose the 10 gallon airbox. I would think any carb off of a 440 size engine should work. Any suggestions? And if I do find one that works, where would I route the tube from the top of the engine, right into the exhaust?
 

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CV is also constant vacuum. But the air velocity is what is used to creat the vacuum, so velocity and vacuum are tightly related. Funny thing is that nothing about velocity or vacuum is constant. It is only the variability in vacuum that make the slides rise and fall. And the speed of air in the carb is not constant either. But I guess that's why noses run, feet smell, we drive on the parkway, and park on the driveway, etc..............
 

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Discussion Starter · #16 ·
Well, I can not seem to resist the call of the pod air filters and have ordered some new jets against all reason. Fortunately the bike came with a spare carb, so if I screw up the first one I have a back up so I can return the bike to stock. The seller of the jets is confident they'll work like a charm and for $39 it's worth a shot. I don't know when I'll get them installed and running since it's starting to get cold in Wisconsin, but I'll be sure to update the post to let you all know the results.
 

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If you are deeply into the carbs look at each and every jet under a magnifying lens too see that all is cool and clean. These carbs are magnificant in their precise construction and deserve the highest order of rebuild attention. No special skill, just work slow and smart.
 

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I know this is an old thread, but if anyone knows how those new jets worked for this guy and where he got them from I would like to know. My 440 was missing all air cleaner parts when I bought it and I went with POD filters and I am having fuel/air ratio problems also. I have been trying to track down a factor air cleaner set up for about a year with no luck and have also thought about fabricating one but if I decide to do that it will be a winter project probably so I can at least ride my bike this summer.
 
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