The following conversion was developed by Scott Potter (m201 no. 13542) in the US. Scott wrote:

This is what I came up with for a dry air cleaner for the 201. First don’t get me wrong, I have nothing against oil bath air cleaners, but the WOF housing has several cork gaskets that I cant get, and it would have taken me longer to make them, than it did for this conversion. I'm not thinking in the metric system today so everything will be fractional. So here we go...
First I needed prints of existing elements so I could find the best one. I found nothing from the major manufacturers, but found this site from K&N Filters who you may have heard of. They have a search function that allowed me to search filters buy dimension. Thus I found this one, its Nappa PN# 2143 that crosses to Fram # CA568, AC# A633C, and a host of others. Its almost the same dimensions as the org. wire bath element.

If you look at the link there is also a Honda part that may be even better, as its closed at one end, but I couldn't get that one today so I went with the NAPA part that you see above. 


I had only one of the original cork gaskets left, and luckily it was the one that the element sits up into in the top of the housing. Without the cork, the element seals quite well, but with it, its seals perfectly.

As I studied the WOF cleaner I found that if you take the bottom support cup off and invert it, it will fit the element and seal quite well, it’s the same ID as the top of the housing (hard to see in the pics)

To make this work, I had to close and seal the vents or louvers in the org. cup. It was easy to first just peen and bend them closed. I thought I would weld them shut, then thought of an epoxy I use in the shop quite often. Its made by Permatex, and called Cold Weld. Its for metal, and I've sealed an old radiator or two with it, and after years its never failed, so I used that, clean and prep the area, and its easy.

To make that set up work I had to lengthen the retaining screw that secures the element up into the filter housing. For that I cut a piece of 1/4 20 threaded rod to 7 3/4 inches, and installed a large area washer and wing nut. (I later replaced the wing nut with a self locking nut.)

I tack welded the rod to the mounting bracket to prevent it backing down in service,

 and installed it back into the housing.

For the other areas I used some sealant, (the gasket at the bottom at the clips is no longer a factor, as there's nothing to leak out), it may not be called for, but I like to go the extra step sometimes, and when I service the unit to replace the element, cleaning the rtv and resealing it will be no issue compared to servicing the old oil bath type.

A 'nylock' self-locking nut and washer hold everything together.

Oops,  the mounting bracket is on upside down in the last two photos - sorry!