Never run your engine without an air (cleaner) filter

Even a good engine can be bad if you use the wrong or no air filter at all.
Never use an engine without this money saver.

Also before you read this all a strong reminder and tip.

Replace foam air-filters when they are dirty! 
A replacing time sequence can not be given because it depends on the track and weather conditions! 
If you have any doubt over the working of your foam air-filter, replace it before it is too late!
Engine builders are strongly advising not to clean dirty single or second stage foam air filters.
They claim that dust particals may remain in the foam after cleaning and will reach the engine next time used. 
This will reduce engine life dramaticly.

We can dived air filters in three types

Foam filters Cotton filters Paper filters

Making first stage foam filters yourself

Foam filters

Some kits come with a standard foam air filter. Normally these filters can be bought as after market product too.
These filters need to be oiled with special air filter oil. 
For the Mugen, SVM Crono, Hong Nor, Thunder Tiger, R&B and Ho Bao filters you can use the original oil supplied with the filter or any other airfilter foam oil or the oil like they use on cross motors containing solvent.
The white Kyosho filter can not be used with this type of oil because the foam is sensitive for solvents. 
Therefore use Kyosho or same type of oil only.

If you are not certain you can always use risinus oil to oil your airfilter.

Foam air filters come in two versions

Single stage foam air filters only have one foam core to filter small and large dust and dirt particles. Dual stage foam air filters have two foam cores to filter dust and dirt particles. 
Single stage foam air filter are made by Mugen, Kyosho, Ho Bao, Hong Nor etc. The first stage is a thinner foam filter that collects the major of the dust and dirt.
The second stage foam filters out the smaller particles.
Two stages filters are made by R&B, Thunder Tiger, SVM Crono

How to oil these foam filters the right way without getting dirty hands?

filter-001.jpg (17772 bytes) A complete dual stage Thunder Tiger foam airfilter unit in parts
filter-002.jpg (18568 bytes) Take the inner filter (second stage) out of the outer filter (first stage) and this is what you get.
Never clean or resuse the "second stage foam filters". 
When they look to be dirty replace them by a fresh one!

filter-003.jpg (17789 bytes) Put the two pieces of foam in a zip bag and put some airfilter oil inside.
The zip bag prevents you from getting dirty hands!
I always use air filter oil that is used in motor cross like Bell-ray, Yamaha or others when this is not provided in the kit.
Associated, Mugen and Crono  airfilter oil are good options too.
filter-004.jpg (20836 bytes) If the oil is massaged thoroughly in the foam it should have an nice equal color. 
When the foam is colored the same overall, open the bag and take out the filter. No light spots may be seen. 
If necessary put some more oil in and massage again.
filter-005.jpg (31901 bytes) Then take an old cloth or kitchen towel paper and massage lightly all excessive oil from the filters. 
filter-006.jpg (22462 bytes) The inner and outer foam ready for use.
If you prepare more then one filter, then put them in a closed zip-bag till raceday.
Before you use them on race day open the zip-bag and take the required filter(s) out so any left solvent can evaporate.
filter-007.jpg (25569 bytes) Let the filters dry for 30 minutes so the solvents can evaporate and then place them on the filter holder.
filter-008.jpg (31166 bytes) Place the end cap on the filter holder and then place the first stage filter too.
filter-009.jpg (20537 bytes) Connect the airfilter connector with a zip ty firmly. Then connect the air filter connector to the neck of the carburator also with a zip-ty firmly pulled.

Replace the foam air-filter when it is dirty! 
A replacing time sequence can not be given because it depends on the track and weather/dust conditions! 
If you have any doubt over the working of your foam air-filter, replace it before it is too late!

Engine builders are strongly advising not to clean dirty single or second stage foam air filters.
They claim that dust particals may remain in the foam after cleaning and will reach the engine next time used. 
This will reduce engine life dramaticly.

Cleaning foam filter is not advised but at own risk here are four simple steps!

1] Take a glass jar and fill it with mineral spirits, just put the filters in the jar and close the jar.
2] Let the filter(s) soak in there overnight.
3] Day after squeeze out the excessive oil and mineral spirits and let the filter(s) dry fully.
4] Put the filters in a washing machine and after the program, let them dry first fully before reusing.


Cotton filters
These are mostly used as after market part.

The most known cotton filter is from K&N
This filter normally comes with red colored oil included.
A K&N cotton has more breathing space as a foam filter and has less air resistance.
Oil this filter until no white cotton spots can be seen.
We adivise if needed to use these cotton filters with an extra first stage foam filter with only oil at the inside.

The cotton filter itself can be cleaned if needed with the special K&N filter cleaner
Always clean with from the inside to the outside of the filter! Never use compressed air to clean this filter! 
Let the filter dry overnight before applying oil again.


Paper filters
These are only coming with some OS-Max engines

It is not advisable to use paper filters only with off-road cars.
These filter have the best breathing capacity compared to cotton and foam filters.
As these filters can not be oiled, small dust particles can enter the engine. 
Always use these paper filters with an extra first stage foam filter around that has been oiled thoroughly.
We advise never to use paper filters in very dusty conditions.

Replace the air-filter when it is dirty! 


How to make first stage foam filters your self?

filter-010.jpg (26681 bytes) The first stage filter can be made by yourself easily. I buy the pieces of foams in pre cut slices form by a store that sells foam in all kinds of forms. They cut the foam in the size and thickness I require. A first stage foam filter cost me 15 Euro cents each. I replace after each heat this filter. If money is an issue then do not throw them away but read further how to reuse them!
filter-011.jpg (26598 bytes) These are all the things needed for the fabrication. Ruler, rubber cement (tixotrope glue), scissor, foam and the airfilter.
I like for single stage filters the foam a little wider as the filter holder itself to be sure we have no air leak.
filter-012.jpg (34323 bytes) Place the foam around the filter and mark at the point where both the foam is over lapping a small cut with a scissor.
filter-013.jpg (24027 bytes) The cut the foam in a straight line.
filter-014.jpg (33016 bytes) Check by forming the foam around the filter. If both ends of the foam are touching remove at one side 2 mm. Try again until the gap is +/- 3 mm. We need a little tight fitting so we make the foam a little shorter as the normal outside diameter of the filter holder.
filter-015.jpg (24107 bytes) Take the rubber cement (tixotrope glue) and apply at both ends of the foam a little glue. Measure the lenght for the next time you want to make more of those first stage filters.
Remember that not all airfilter holders are the same in diameter!
Do not use to much glue as the glue hardens this hard part may cause an unnecessary air leak.
filter-016.jpg (25008 bytes) Let the glue dry 8 minutes and the press both ends together.
filter-017.jpg (21870 bytes) Then put the foam around the air filter holder and check for sleek fitting around the airfilter holder.
filter-018.jpg (21631 bytes) Also check the other side for sleek fitting around the airfilter holder.
filter-020.jpg (26049 bytes) If you think the filter is made to wide cut some material away at one side.
We advise to use always a foam that is a little wider as the air filter holder itself and is overlapping the edges.
filter-019.jpg (20926 bytes) You can apply in de same way as the second stage foam filters some air filter oil on this filter depending on the circumstances of use.
You can reuse these self made first stage foam filters or those that come with with two stage foam filters simply by first cleaning them with washing petrol and let them dry.
Then put them in a cotton bag and put them in the washing machine at maximum 40 degrees. Your first stage foam filters will be as new and can be reused.
 
However never clean this way "second stage foam filters or one stage only foam filters". When they look to be dirty replace them by a fresh one!