Roll Your Own Air Filters

You might all know this already, and if you do I apologize in advance. But if you don't here is a way to make your own oiled-foam air filters.

I learned some years ago, a pretty useful trick. Buy some UNI air filter bulk foam. Local motorcycle shops will order it for you or go online. It's cheap and comes in sheets of green foam. Get out your sharp scissors and make whatever parts you need.

The secret is clear silicone RTV adhesive. It will permanently glue the air filter foam to itself. To make this one for my Urban Express, I cut a piece to fit around a 1-inch diameter pipe, glued it and held in place with painter's tape until it dried in a couple hours. Then I made a round piece for the end and glued that one.

This kind of foam needs to be oiled to be an effective air filter. So I shot it with a few blasts of aerosol Spectro Foam Filter Oil. Pretty much any kind of oil will do in a pinch. Clamped it on with a zip tie because I didn't have any clamps small enough. It's not pretty but it will work great for a long time if I need it to. Better yet it's washable and re-oilable and it cost almost nothing to make.

Pretty cool, huh? (edited)


Re: Roll Your Own Air Filters

hah! I'm so pumped this is on an urban express too. I came up with some sily filter ideas on mine.

I've used RTV silicones on filters before and had issues. just for fixing filters that tore or whatever. after a while the silicone would break down and start falling in, got little bits caught in the carb and reeds, probably digested plenty. nice thing is it's soft enough to be mostly harmless but it doesn't hold up well to gas, and any engine, especially piston port is gonna get pretty gassy in the filter.

Things that might work better but I've not tried in that application are like Seal-All or Goop automotive maybe? I've used Permabond forgasket stuff cuz it's great for gas resistance but I duno if it has much adhesive strength

Re: Roll Your Own Air Filters

jonathan alvarez /

I use superglue to bond foam in a homemade air filter, 6 months and is still holding pretty well

Re: Roll Your Own Air Filters

Using actual air filter foam and RTV results in a filter that can be used for years. RTV on clean, un-oiled filter foam has permanent adhesive strength.

As such these filters can be washed, re-oiled and used again. The Honda filters for my SL350 have not been available for many years. There are two large foam sleeves, on for each carb. Very simple to make. The ones I made for this bike, possibly in 2013 still look and perform as new. (edited)

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