Topic: Washing a Stock OEM CB350F Air Filter

[wdhewson]

Hi:

Fixing up a somewhat tired 1972 CB350F. 

The OEM airfilter looked pretty good but did have some "junk" on the filter medium.  So I got a big bucket of hot water with dishwashing soap and agitated the filter around in this solution repeatedly and with vigor.  Not that much dirt came out.  Repeated this wash cycle, and only a few specks were in the bottom of the white bucket.  Then flowed hot clean water from the inside to the outside of the filter.

The filter now sits drying on the hot air register.

What do you think?  Will this filter be good as new or did I wreck it?

Don

[MasterChief750]

paper filters are replaced not usually washed and reused. id buy a new one.

[Gordon]

You can't wash and re-use a paper filter.  When it's dry the paper fibers will probably be completely mashed together and will only allow very little, if any air to flow through.  New filters are available and don't cost that much.

[wdhewson]

Thanks guys. 

The filter seems to be made of some type of fluffy cloth, and not a paper material.  But I'm guessing a bit here.  Even if it were a paper filter element, would it be stabilized with something to give it water resistance which might be needed for rain, humidity, bike washing, and the like?  However, nothing like new parts.  Don

[Deltarider]

The filter seems to be made of some type of fluffy cloth, and not a paper material.  But I'm guessing a bit here.

Just take a magnifying glass and have a look at it and you'll see the material is far from fluffy. There are some misunderstandings about paper filter airelements. I've read in a overall well informed French manual that you can wash and dry them, but I doubt the result will be good. I will try this with an old element as soon as I start riding again (too cold now). Anyway price for OEM is reasonable and you'll have the best filter medium.

[wdhewson]

Thanks. 

What should I see with a magnifying glass?  A bunch of random or non-oriented fibers like expected in paper, or the highly regular weave of a textile? 

Going to get my glass right now?  Don.

[Gordon]

It's paper, so it should look like paper.  If it looks like a woven fabric then what you have isn't the stock paper filter. 

[Deltarider]

A bunch of random or non-oriented fibers like expected in paper

Correct (that is if I understand your English well).

[mgbgt89]

On cb200t's, which the air filters are NLA, People burn out all the paper and glue off the metal housing, then glue UNI foam in it. I've heard it works well.

[wdhewson]

Under the magnifying lens the filter medium does not reveal any thing but a fluffy felt like surface.  No woven textile characteristics, but it sure doesn't look like paper either.

Th filter says HM air filter Honda CB350F and CB400F, so I'm concluding it is Honda OEM.  But what do I know, as I'm new to SOHC4s?

I left the washed filter on the warm air furnace vent for 2 days, and it was light weight and dry.  So I did the following "scientific" flow test.

Our house has powerful two stage central vacuum system for carpet vacuuming.  So I rigged a plate to cover the filter mouth facing the carbs and sucked air through the filter with the central vac.  There was absolutely no tendancy for the filter assembly to be sucked down on the plate as you might expect if partially clogged.  Also, and maybe most importantly, there was no change in "pitch" from the central vac's whining sound.  And the ear is very sensitive to pitch in this audible range.  I conclude that no suck down and no pitch change amounts to freely flowing filter after washing.

Do you think my 2-stage central vac flows as much air as a full throttle CB350F?  I don't know?  Opinions on this question and all the above are valued.  Thanks, Don.

[scottly]

Is it possible you have a K&N type filter? Cotton gauze sandwiched between metal screen, oiled with a red colored oil?

[wdhewson]

Nay, she's not a K&N.  I know their construction well. 

I'd take a picture but haven't been sufficiently patient to learn how to post images.

[crazypj]

You have original filter that someone has already washed.
 The fibers swell and look like felt.
 No change in pitch suggests it wont filter very well as there should be some pressure drop (or your central vac isn't up to snuff?)

[Deltarider]

You have original filter that someone has already washed.

+1 You should see individual fibers in a good one, I believe.

True testing however is in comparing a new filter (OEM) with an used one or an imitation filter as described in:

http://forums.sohc4.net/index.php?topic=47771.0

To my knowledge nobody performed this simple test yet.