Hey all! So I've been searching around for more info on this custom airbox for a while now and it seems as if the OP is MIA haha. I even went as far as to find my way to his website and tried emailing him but hadn't received a response. Hopefully he is somewhere enjoying his kz440!

Anyway, since his original posts from years ago provided enough information for me to wrap my head around the basics of this airbox build.... I figured I'd take the chance, build one for myself, and gather the last pieces of the puzzle in order to make life easier on other kz owners who want to build one but weren't sure about the missing details.
Here is a summary of my journey so far:
The OP seemed to know a lot more information than I do about the factory airbox flow etc so I purchased the aluminum air box from Amazon that he recommended as well as the short air filter he recommended (it was for a moped haha). He also used the rubber boots that would have gone with a factory airbox. They have a special taper and are slightly angled which made fitting this airbox on the bike work. I was lucky to find some on eBay for $20. With straight boots or radiator hose etc. it probably would've been a bit harder to get it to fit right. That said… It was still a tight squeeze and a bit of stretching was needed in the end to get them to fit over the carbs from their position on the airbox. The reason why? Because the aluminum box, while it does fit between the frame rails, is just barely big enough to allow enough width between the holes I drilled for the boots to fit over the carbs. I drilled the holes for them to be as far apart as possible while still giving them enough space from the edge to make a good seal. It was a tight squeeze getting them to fit but it worked. I used a 1 3/4 inch hole saw to drill the hole in the front and two holes in the back of the aluminum box. The holes were a perfect fit for the carb boots in the back. Make sure to sand them a tiny bit after drilling to make them smooth as The freshly drilled holes were sharp and could cut the boots after a while if not sanded. I used a plastic 1 1/2 inch trap adaptor from Home Depot (plumbing section) to attach the filter to the front of the box.
The OP might have mounted their adaptor with epoxy or something else but I wasn't sure so I bought the trap adapter that has threading on one side. Then I used a grinding bit to open up the hole a tiny bit on the front in order to screw the threads from the trap adapter in. I then used the cap from the back of the trap adapter to secure it to the box and didn't need any glue or epoxy. The cool thing about this approach… You can either use the 1 1/2 inch wide cap that came with this adapter or buy one that's 1 1/4 inch wide (from a 1 1/2 to 1 1/4 step down adaptor) that still screws onto the original threads. This could come in handy if the engine is still getting a bit too much air. I'll be able to dial it in once the bike is completely safe to ride (still needs brakes and fork seals etc). In one of my photos, you'll see the 1 1/2 cap next to one that is 1 1/4 for comparison.
I'm not sure what the OP used to seal up the box but I've just used electrical tape for now as a temporary seal incase I need to tinker with it some more. I'll also add the brackets to it to mount it to the frame when I get a free day. It also looks like the OP used a round Tupperware cup as a windscreen. I'll prob add one as well once I get a chance. When I started the bike it fired up in a half of a second and purred like a kitten immediately. It has never sounded as good. It idles stable. I took it out on my block and rode it up and down a couple times just to see what it was like to run through the range of RPMs. Before, it would stumble over itself from 1/4 throttle and up. Now, smooth as silk. I'm attaching pics so you can see what I saw. Feel free to contact me with any questions. I'll give more updates if I find anything new as I go!
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