TDM900 : Adapting a car air-filter element

Why using a car air-filter element ?

There are only two ways to increase the total airflow passing through an air-filter :
1 - increase the surface.
2 - increase the porosity.
The second method is used mainly with second market air filters (K&N). It is ok as long as you don't ride in dusty area or don't plan to keep your bike too long.
In summary : greater porosity -> more dust -> engine wears faster.
These filters are well known to the public, they are available at excessive cost, but someone has to pay for all the ads... On the other hand these filters are reusable - which lowers the total cost, unless you sell your bike. You may also buy some "special air-filter oil", at the same cost...

I chose to use method 1 for the renewal of my filter : I bought a car air filter element and trimmed it to fit inside the airbox filter of the TDM.

Some calculation about the air-filter efficiency :
• The TDM900 engine have a breathing rate of : 0.9 x 8.000 / 2 = 3.600 liters per minute at max revs.
• A 2.0 liters car engine have a breathing rate of : 2.0 x 6.000 / 2 = 6.000 liters per minute at max revs.
• with an identical footprint, the car air-filter is twice as thicker : 40mm or more instead of 20mm on the genuine air-filter.

Finally, there is a double advantage using a car air-filter element on the TDM :
• better effectiveness, approx. twice as better.
• cost, approx five time lower...

On the other hand, some do-it-yourself skills are essential, however you're on the right place.

Before you start

• Skill level required : average, may be difficult to adjust and to get perfect air-tight.
• Timing : about two hours.

Tools & parts

• A cutter, a small saw, a set of files / electric file.
• A hot-glue gun, or a Sikaflex gun - silicone sealing don't stick well.
• A car air-filter element : 160mm x 218mm x 40mm (or less).
As it's almost impossible to find an element that fit perfectly, it's best & easiest to find one with the right width : 160mm.

Reference :
• Carrefour A05 - good width, a little bit too long, thicker than the support but it fits.
• Carrefour A60 - correct size, perfect thickness, easier to adapt.

First steps

To gain access to the air-box, you need to :
• Remove the seat - the easy step.
• Remove the side fairings.
• Remove the black plastic covers under the tank.
• Remove the two screws at the front end of the fuel tank.
• Rotate the fuel tank backward until there is enough space under it then secure it.

(image)The air box can be accessed.
Untight the eight screws of the upper part & open it.

(image)Remove the air-filter element, blank the two air-ducts.
You may then clean the lower part of the air-box with an oily rag.
Check at that point that the air-ducts are well fitted on the injector's bodies.

Modding the oem airfilter element frame

(image)Now this is point where this poor air-filter goes under surgery.
Cut out all the paper element with the cutter.

(image)Get rid of the underneath metallic grid with the help of the electric file.
Take the saw and cut out all the plastic holders, the aim is to get a neat rectangular frame.
Finish with the file.
Clean the plastic frame, there must be no dirt nor grease on it if you want perfect gluing.

Fitting the filter - type A05

(image)The new air-filter is too long and needs precise cut-out.
Place a length mark with a pen, then cut it carefully with a cutter.


(image)Insert the air-filter on the underside, the orange border stays outside.
The air-filter will not be exactly straight, this is not an issue.

(image)With the glue gun pour enough glue on the four edges, with a special attention on the edge without the orange border.
It is required that the gluing of the air-filter on the plastic frame be absolutely air-tight.

(image)Wait for the glue to cool down, then fit the filter element inside the lower air-filter box.
The orange border near the rear part of the frame may be too close to the edge and therefore may need some trimming.
As the new filter element is somehow thicker than the genuine one, closing the upper air-box part may be uneasy, requiring some additional trimming / slight upper push.
Anyway my element was 50mm thick and did not need too much adjusting / swearing.

Fitting the filter - type A60

(image)This filter has almost the right size. Just add a small layer of foam (see right-hand side) and trim corners on the left-hand side.

(image)The filter height is correct.

Finishing work (optional)

While the air-box upper part was removed, I took the opportunity to remove the air intake flap & actuator mainly to get more room for the air-filter element and also because it was useless. Removing the flap also allows a better airflow into the air-box.

In the eventuality you need to replace the flap it is advisable to remove it carefully.
I used a milling tool to remove the seven plastic soldering pins :


Replace the air-box upper part & tighten the eight closing screws.
Notice how the air-filter element is much more accessible to the air flow - with the bonus of the top hole left by the actuator.


Last step

Place the eight upper air-box closing screws, replace the gas-tank, fairing and seat.
Start your engine, enjoy the power and go for a ride.

Some usefull reading : debunking the Myths

K&N Air Filter Review - Debunking the Myths (and why OEM is better)

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