After  my NX650 stopped running in the Coronado National Forest I became aware that there was an air cleaner problem.  The problem is that it is a paper element filter and it doesn’t tolerate dust.  I struggled with this for a long time, bought a couple of  new ones at $28 each, looked for a foam filter from Twinair and UNI (none were available) and even bought two K&N’s (they didn’t fit).   I was getting aggravated.  I finally decided to make my own foam filter. 

I had the old Honda filters, so I pulled all the paper out of one and very carefully cleaned out all of the glue that was used to seal the edges of the paper.  When the glue was gone  the two ends separated from the sidewall.  With the parts separate I was able to get every last bit of the old glue out.  I then re-joined the clean parts using silicon sealant (RTV), carefully removing all the excess on the inside so the foam would have a smooth surface to seal against.

Getting the foam was easy.   UNI sells a sheet of foam that is 12x16x5/8 inches, enough for two or three filters.  This is UNI part number BF-1 and retails for around $13.  You local dealer can order it for you or you can order it direct from UNI. 

I cut a strip the foam a little wider than the filter was tall so it would fit firmly against the top and bottom of the filter without buckling in the middle.  The length was selected so that it would fit inside the newly made housing with the ends overlapping about 3/4 inch.  To get a better seal I trimmed the ends as shown.   Again I cut it a little long to  be sure the ends stayed together.

FOAM

To help retain the foam I used some wire mesh and rolled it to form a cylindrical spring that is compressed, inserted inside the filter and allowed to spring out lightly against the foam.

FOAM RETAINER

So how does it work?  It must be better, because now I have to use the choke to start the engine….and there is no dirt on the carb side of the filter.