Air Filter Discussion

[gn83tm]

I have some questions about air filters and which type and cleaning method is really the best for a dirt bike.

I have been bothered with the standard cleaning methods for the typical foam filters for quite a while. Standard procedure seems to be immersing the filter in some sort of solvent (filter cleaner, solvent, kerosene, etc) and breaking down the oil to release the dirt that is trapped in the filter (and oil). My concern with this is that once you get the oil and dirt in suspension in the cleaning liquid isn't the dirt in solution with the liquid and therefore able to reach the carburetor side of the filter? If you just let the filter dry and re-oil it isn't the dirt just waiting to flow into the engine?

Back in my car racing days, the filter of choice was the K&N which is an oiled, cotton, gauze sandwiched between stainless mesh. All the flow tests I remember seeing showed it out-flowing foam and paper elements while at the same time providing better filtration than those media. The filters are cleaned by spraying on a cleaning solution, letting it soak, washing it from the inside out, letting it dry, and re-oiling it. I know K&N filters are available for many bikes. Has anyone had any experience with them?

Foam filters similar to those on dirt bikes are kind of a joke in the auto racing business but maybe I'm missing the reason they are the preferred choice for dirt bikes. From my auto racing background, I would think that a K&N or even a good paper element would be more efficient flow wise and filtration wise. It sure would be nice to be able to buy a good paper element for my KX for less than $5 and just chuck it in the trash when it gets dirty. This would eliminate any chance of getting dirt particles on the carb side of the filter.

Any feedback would be appreciated. Hopefully we can all learn a little bit. Thanks!!

 

[Chili]

I have been bothered with the standard cleaning methods for the typical foam filters for quite a while. Standard procedure seems to be immersing the filter in some sort of solvent (filter cleaner, solvent, kerosene, etc) and breaking down the oil to release the dirt that is trapped in the filter (and oil). My concern with this is that once you get the oil and dirt in suspension in the cleaning liquid isn't the dirt in solution with the liquid and therefore able to reach the carburetor side of the filter? If you just let the filter dry and re-oil it isn't the dirt just waiting to flow into the engine?

I beleive your missing an important step in the process. I basically dunk the filter in kerosene very briefly to help break down the oil and make it easier to wash out of the filter. The filter is then washed in warm soapy water and rinsed several times until the filter is clean. Then it is allowed to dry before being oiled and reused.

 

[gn83tm]

That is basically the method I use also. I wash the filter in the parts washer to break down the oil and then wash it in the shop sink in soapy water to cut the solvent and then rinse it off in running water to get rid of the soapy water. But I usually see weed seeds that are imbedded in the foam and only come out if I pick them out. Don't you suppose dirt particles are hiding in a similar manner?

 

[soap]

I have the UNI dual foam filter, and I have never had to clean the inside filter. The outer layer catches all the dirt and when I wash it I just make sure to rinse the hot water from the inside to the out. That way the dirt and oil are pushed out instead of forced inside. I think the reason that dirt bikes use foam extensively is because if you look at the size of the foam filters compared to the gauze filters in quads, there is a lot more surface area for the air to pass.
Just my two cents.

 

[sloopy]

what do you guys use to re oil the filter?

 

[gn83tm]

Soap; I use the Uni filters also but always clean both elements. The outer element is quite coarse so most of the fine particles of dirt probably end up in the finer, inner filter. The outside usually has a lot of larger particles and weed seeds.

The flow bench comparison tests I have show a Unifilter flowing 4.5 cfm/sq in, a paper filter flowing 5.2 cfm/sq in, and a K&N flowing 6.5 cfm/sq in. Looks to me like you could run a lot smaller K&N or paper filter and still get the airflow you need. The same test showed a K&N after the Baja 500 flowing 5.1 cfm/sq in. It was covered with up to 1/4" of dirt over its entire surface. The tests I am referencing are from a book titled "Performance With Economy" by David Vizard.

sloopy; I use the nasty, sticky, hard to get off your hands, filter oil from Bel-Ray.

 

[bcVulcan]

PJ1 or Maxima, Fab1 work really well. If you've never used these types of spray on oils, I'm sure you'll be hooked once you do. I used to be in the dark, and used motor oil, but once you see the consistancy of the spray on oils, you'll understand why we all pay five or six bucks for the good stuff.
I keep a three gallon bucket of kerosene with a lid on it out behind my shop to rinse my filter out. I haven't changed it all year and it's still clean. (dirt goes to the bottom) Wash with soap and water and your ready to go. This is so much easier and faster than trying to wash it without the use of any solvents, it makes me do it more often.

 

[snb73]

gm83tm,

Paper filters aren't a good choice because they would fall apart and be useless once they got wet. Filters for off road bikes are meant to be cleaned almost every ride. A clean filter is cheap insurance for your engine.

I'm sure we all have our own method, but here's what works for me.

Clean the filter in your choice of solvent to remove the old oil and dirt it trapped. I use gasoline. I prefer using a small bucket with enough solvent to submerge the filter. Knead the filter a few times, sqeeze out the excess, dump the dirty stuff. (it's great for killing weeds growing in the driveway cracks) Repeat 3-4 times or until the solvent remains clear, and you can't feel any dirt in the bottom of the bucket.

Wash the filter in warm soapy water. I use dishwashing liquid. (dawn, joy ect...) Use the same bucket and method as with the solvent, just use warm soapy water. Repeat 3-4 times, sqeezing the filter and dumping the dirty water each time.

Rinse in warm water. Same method. Dump the dirt water each time. Repeat until the soap bubbles are gone. Their shouldn't be any dirt particles in the bottom of the bucket.

If the dirt is really imbedded in the filter I use the garden hose or the kitchen sink sprayer to remove it. Spraying from the inside of the filter, the water pressure pushes the dirt out the way it came in. I hold the nossle right up against the filter. Gentle pinching and kneading will get it all out.

Once the filter is clean, I spin dry (no water) it in the washing machine. Set the filter so the centrifigle force pulls from the inside out. (have the side that faces your carb, face the center of the washing machine)
If the filter won't sit still, I prop it with a clean shop towel. It should be dry in a few hours after that.

Before oiling, I turn the filter inside out to see if I missed any dirt. "Plucking it" with your finger almost always removes it.

Don some latex gloves (found at home depot in the paint section). Place the filter in a clean bucket, pour the filter oil all over it. I use an 8X8 inch plastic bucket with a lid. Saturate it with your favorite oil, sqeeze out the excess and install. I don't grease the rim. You will have alot of oil left in the bucket. It's clean, so pour it back into the filter oil can to use next time. I use Twin Air filter oil.

This method only takes about 15 minutes, minus drying time of course. I clean my filter about once a week. I've used this method for a year and a half with no adverse effects to the Twin Air filter.

Hope this helps, Steve.

 

[CaptainObvious]

I have been bothered with the standard cleaning methods for the typical foam filters for quite a while. Standard procedure seems to be immersing the filter in some sort of solvent (filter cleaner, solvent, kerosene, etc) and breaking down the oil to release the dirt that is trapped in the filter (and oil). My concern with this is that once you get the oil and dirt in suspension in the cleaning liquid isn't the dirt in solution with the liquid and therefore able to reach the carburetor side of the filter? If you just let the filter dry and re-oil it isn't the dirt just waiting to flow into the engine?

I don't like cleaning with solvents either.

Tell me gn83tm, are you bothered by water? There is a cleaner and oil system that is based on vegetable oil. It works great. But rather than me spending the next 15 minutes explaining it...I'll let the web-site do that for me...

http://www.notoil.com/

 

[gn83tm]

rv6 I don't have any adversions to cleaning with water or solvents or anything else. As you see in my first post I use plenty of each. What I am "bothered" about is dunking the filter in a solution that breaks down the oil and puts it and the dirt it carries into suspension in the cleaning liquid. This stuff then has a chance to become imbedded in every area of the filter - inside and out. If it doesn't get rinsed out it seems to me that it's just waiting to get sucked into the engine.

The NoToil system is similar to the K&N system in that you use a cleaner and water that is particularly suited to the oil that's used. Correct me if I'm wrong, but with the NoToil way aren't you still dunking the entire filter in the solution? With the K&N's we run on the race cars you spray the cleaner on, let it sit to loosen things up and then wash with water from the inside out which keeps any dirt from getting on the inside. I suppose this same basic method could be used on the foam filters also.

snb73's comment about the paper filters and water is a good point and is probably why we don't see them on dirt bikes although there's quite a few cars driven in the rain every day without much problem.

I'm not really looking for the perfect foam filter cleaning method here. I'm more looking for a decent discussion about alternative filtering methods and why we don't see more of them. It was just something I was thinking about last night when I was out in the shop, spending what I thought was too much time, cleaning filters for mine and the kids' bikes. Just something to think about. Thanks for the replies!

 

[CaptainObvious]

What I am "bothered" about is dunking the filter in a solution that breaks down the oil and puts it and the dirt it carries into suspension in the cleaning liquid. This stuff then has a chance to become imbedded in every area of the filter - inside and out. If it doesn't get rinsed out it seems to me that it's just waiting to get sucked into the engine.

The NoToil system is similar to the K&N system in that you use a cleaner and water that is particularly suited to the oil that's used. Correct me if I'm wrong, but with the NoToil way aren't you still dunking the entire filter in the solution?

You are correct, the filter gets completely submerged in the cleaning solution, however, I use multiple rinse cycles to I don't have to worry about dirt being lodged in the filter. Moreover, when I rinse the filter, I do so by running water from the inside-out.

If you believe that this still leaves too much dirt in the filter, I'd suggest that you look into Ready Filters....

http://www.readyracing.com

...this way you can have a fresh filter when ever you want it. If you look at the cost of a new filter, plus all of the chemicals required to clean & oil it...the Ready Filters are a decent value. Plus you have the added piece of mind that there isn't any embedded dirt in the filter.

 

[biglou]

Hijacking thread for a minute... Speaking of air filters, I have one for you Gary. Oiled and ready to go. It's a Uni dual element, brand new. I have three total, and I got them for cheap, so it's yours. I may get it on the baby piglet before you get there depending on how busy we are. :cool:

 

[matt-itude]

so the base question here isnt about cleaning its about why a foam filter instead of paper or gause?

 

[CaptainObvious]

Thanks Lou....now back to the debate...

 

[gn83tm]

matt;
That's more what I was getting to and the reason I originally posted this in the mods and performance forum instead of the general maintenance section. The moderator must have misunderstood me also and moved the post here. Sorry if I wasn't clear the first time.

I know we can debate the proper way to clean the standard foam filter all day and there have been many threads doing such. I was really just looking to start a discussion about alternative filters given some of the drawbacks of the foam units.

 

[motometal]

regarding dirt migrating towards the inside of the filter...consider the velocity through the inlet (filter side) of the carb. now divide that by the area of the filter. Ok, is a gentle breeze, not a hurricane. Now consider the adhesive power of the filter oil you should be using.

My point? Even if there is a particle of dirt on the carb side of the filter, if it's oiled properly, that dirt isn't going anywhere!

spray on filter oil: great if you use enough to actually saturate. It's hard to beat the method of using a plastic bag and working it into the filter.

latex gloves break down when used around solvents, gasoline, etc. You should be wearing nitrile gloves from the moment you start handling the filter. Some of the same components in that gasoline that make your hands stink are also going right into your bloodstream by diffusion, and then to your liver, kidneys etc.

spread grease on the inside of the boot between the filter and carb. this will catch dirt if for some reason it does slip by, and will also give you an indication of filter effectiveness.

No need to rinse the dirt out with the solvent, just use it to dissolve the oil...then go right to the warm water/Detergent to really get the dirt and grit out.

Avoid putting extra pre-oiled filters in sealed plastic bags, the carrier solvents in some filter oils will break down the foam over time. It needs to breathe.

You can use an old bath towel to absorb away the water in between washing and re-oiling. No need to hang up the filter and wait for hours.

 

[ginster77]

i don't know why people don't use paper filters on big bikes, you can buy them for any street bike and i see all kinds on the tricked out fiddys. maybe because of water when washing or creek crossings. but street bikes ride in the rain, i don't get it either. maybe your on to something, better put a patent on it quick before someone gets rich off it before you..

 

[Uchytil]

Whoa Pardner

I've been cleaning airfilters for me and my boys for 30 years and have never seen a catastrophic failure based on the format of how air filters were cleaned. I've got barrels that the kids rode with one top end a year that are over 10 years old that still have crosshatch. I started with gasoline in my teens and worked up to kerosene mixed with parts cleaner. My most recent change is NoToil. It's the best thing since sliced bread and yes I still soak the whole filter in the cleaner and rinse it sevearl times, just like all the years before. The great thing is I buy the cleaning solution at the grocery store for pennies on the dollar because it's 100% the same stuff NoToil pacakges (MSDS confirms). My son's still use BelRay but and it's all good but they come over eventually. Worry warts! Get out and ride!

 

[David Trustrum]

Motometal makes the points going on in my mind re the gas vs skin & the nitrile gloves, & another one re spare pre-oiled filters, thanks I’ll stop doing that.

K&N filters work real well, use them in my streetbike. Probably cope with dusty conditions ok, but mud & water they won’t be real tolerant of. When people used to put individual filters on streetbikes they often got clogged with water if they were exposed & it was really raining. Airboxes remove this problem, but they don’t do many stream/bog crossings.

O work on the theory that there’s no point having your filter dripping. I turn the filter inside out & apply the oil with a plastic squeezy bottle & kneed it in & repeat the procedure several times.

I have heard that spray oils are so thin that they are not effective. Whether that is true or not I wonder.

 

[XRpredator]

. . . The great thing is I buy the cleaning solution at the grocery store for pennies on the dollar because it's 100% the same stuff NoToil pacakges (MSDS confirms).

oooh, spill the beans! I have lots of the oil, but would like more cleaner!

 

[brentl]

All knowing fortyplus!!!!

Please tell us what u buy for cleaning!! :worship: :worship:

 

[Uchytil]

Here's the stuff

Biodegradable Foam Filter Cleaner lists Sodium Carbonate (CAS#497-19-8) AS THE 100% ingredient in their MSDS. A quick search of common names is "Sal Soda, Soda Ash & Washing Soda. Arm & Hammer (I am not affliated with in any way) packages Super Washing Soda (UPC 33200-03020) which also is 100% Sodium Carbonate. You have to make sure you are not buying Baking Soda fellas, be sure it's the right stuff.

If you are interested in what the oil is you can get the MSDS by asking them. It's a good idea in case you decide to swallow some, LOL. Seriously, where I work we have every chemical on file in case someone decides to spray it in their eyes and we need medical attention. The MSDS is also good for finding out what something is made of.

I also checked the Twin Air cleaner but it is composed of multiple compounds although it includes some Sodium Carbonate.

Someone complained once that I was too cheap but I use the cleaner more than the oil. I use the cleaner in my airbox, on my hands, in the washing machine, etc.

No-toil is sooo good right now. But, I may get into the new pre-oiled filters if I hear better reports on them.