Throttle Junkie Tech

Custom Air Cleaner Covers At Bare Knuckle Choppers

Article By: Paul Wideman –

Originally Published In The April 2012 Issue Of Cycle Source Magazine


Okay, so I realize this is one of those tech articles you probably can’t do at home. But like I’ve said in previous writings, if you can take away one tidbit of info, or at the very least find some inkling of entertainment, I have succeeded. So, let me give you some background on our air cleaners. We have sold our Glass Jaw Velocity Stacks for over five years now, and they have proven very successful. But quite often a customer requests something with more filtering, and also wants the apparatus to be small and aesthetically pleasing. There aren’t a whole lot of options out there, so we took it upon ourselves to make one. In Sturgis 2010, Nic and I met with the good folks at K&N. I knew if we were to offer the best air cleaner out there, we had to have the best filter in the world. K&N was more than accepting, and offered up their entire catalog to us. We chose a whole bunch of different shapes and sizes, and decided to start with an element that measures about 4.25” in diameter. This size allows plenty of flow for the demands of the modern (and antique) v-twin powerplant, but is still small enough to not overpower the look of the right side of your scoot. Back in the shop we designed a handful of options and designs and whittled it down to a smooth dome style cover and a ribbed cover. A very simple and maintenance free fastening system was incorporated to keep installation easy. We currently offer these for S&S Super E&G, Super B, as well as SU Eliminator and Bendix carbs. We will have bolt-on kits for many CV carb configurations, including Sportsters, hopefully by the time this article goes to press. I’ll give you an idea what goes into making one of these…


After cutting what feels like a small fortune’s worth of aluminum in the bandsaw, I face one side of each puck in the manual lathe.


I head to the CNC lathe and load the puck in the chuck. This puck will make a cover piece.


After the lathe faces the saw cut side of the puck, the machine begins to drill the piece: first a center drill, then a .257” drill, then a 7/8 drill to give clearance for the boring bar.


Now the boring bar goes to work. Here you can see what the back side of the cover will look like.


When the boring bar is done, the piece is ready to be removed and the flip side machined.


When the second side is machined, the thin walls of the cover can be crushed by the chuck jaws. To prevent this, I have to either reduce the pressure of the jaws, or support the piece from the inside. Based on past experience, I like to keep the jaws at a specific pressure, so I opt to use a machined puck that is only a few thousandths smaller than the I.D. of the cover. This prevents the jaws from crushing and deforming the cover.


The next process starts with an endmill making a flat face where the cover bolt will seat. The endmill is offset and only makes a shallow cut. The boring bar follows up and adds some radius to the area.


Now the general turning tool starts to shape the outside of the cover. It makes very large, general cuts in the first pass.


And in the second pass, the tool makes a very smooth and fluid pass that makes the final profile.


Aside from a very light finishing pass on the manual lathe to remove any holding marks, this piece is done and ready for coating/ plating.


Here you will see the thicker “ribbed” cover on the left, which will be sent to the CNC mill for further machining, and the thinner “domed” cover on the right which is done.


This process is pretty simple; a 3/8” ball endmill makes 3D passes from left to right creating the ribbed look.


Ready for deburring and a final cleanup on the manual machine.


We waterjet the brackets with the bottom surface along the mill edge of the aluminum stock. This gives us a perfect edge that does not need to be machined.


The top side is however, waterjetted, and has kerf marks and a stem that must be removed in the manual mill.


A quick program is run in the CNC mill that mills the edges flat allowing a center drill and a .201” drill to do their work. Normally I would tap these in the mill as well, but my tapping head was being repaired, so we had to do this run the old fashioned way.


In our shipping/assembly room, I grab all the necessary parts and pieces to assemble one of the kits that is being shipped raw.


First the bracket is bolted to the backing plate, this one has an S&S Super E backing plate, using two flat top bolts.


After placing the K&N filter, I place the cover over the filter, then using the stainless steel 12pt ARP bolt, I fasten the entire kit together.


Assembled and ready to ship. In addition to raw, we also offer these in chrome and black.


Like I said, we will be offering many different applications for these, and we will also have some new variations in the future. If interested, please call or write. 1-888-240-NUKL or Until next time, FTW! Paul

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