TDM900: Cleaning the fuel tank / fuel pump


Gasoline is extremely flammable, volatile, toxic and carcinogenic, all precautions must be taken to ensure safety :
• Work in a ventilated area, wear protecting goggles and gloves.
• Banish any sources of heat, flame, spark, etc.
• Nobody smoking nearby, no children nor pets.
• Do not improvise anything, prepare everything in advance.
• Do not undertake anything before having understood the whys and the hows.
• Get a suitable container to drain the fuel tank.
• Get rags ready to wipe leaks & spills, get a lidded bin to discard them.

Why clean the tank ?

Over time, a fuel tank accumulates many other things than just fuel :
• Impurities present in the tanks of petrol stations and finding their way into your own fuel tank despite the filters included in the pumps. This may also includes water.
• Fuel decomposition : modern fuel is a mixture of hydrocarbons whose stability over time is not great. If the bike spend the winter in the garage, fuel inside the tank degrades and forms sticky / waxy deposits on the walls and bottom of the tank.
• Condensation 1 : moisture from the air inside the tank when it is not top-filled will form a condensation layer on the walls. This will react with the steel and turn to rust and then into thin rust dust.
• Condensation 2 : water from the condensation process will form a thin layer at the bottom of the tank from where it cannot evaporate - water is denser than fuel. The fuel pump takes this into account, it is located slightly above the actual bottom of the tank. As the layer get thicker with time, some water find its way into the fueling system.

Several problems will then appear:
• The fuel filter clogs slowly along time. The fuel pump is then unable to provide proper fuel pressure to the injectors, resulting in a series of problems : mixture is too lean, engine firing is difficult, rough idling, loss of power, etc. The fuel pump itself is at the risk of excessive heating, mainly when the fuel level is too low to cool the pump.
• Despite the presence of a fuel filter, the thinnest impurities will pass through into the fuel hose and then into the injectors where they will accumulate. Dust and wax will then clog the injectors, requiring them to be changed or cleaned. Fuel mixture problem will also appear.

Removing the tank

Before removing / cleaning the fuel tank, it must be fully drained.
Important : The fuel tank must be half empty or less before draining it. Otherwise some fuel will leak through the vent hoses when raising the tank.


• Remove the seat.
• Remove the fairing sides.
• Remove the two small black side covers.
• Remove the two screws securing the tank to the front.
• Raise the fuel tank backward to get enough room to access the fuel pump pipes, secure with a strap.

Draining the fuel tank

(image)• Get a hose with an appropriate diameter to fit the fuel outlet on the fuel pump and enough length to go inside the spare tank.
• Remove the hose out of the gas pump, unlock by pinching the plastic end and pull.
• Do not use brute force on the outlet of the pump, it is a fragile part : in case it breaks you'll need a new fuel pump.
• Be careful, some fuel may spill from the pump outlet, depending on the fuel quantity remaining inside the fuel tank.
• Replace the fuel tank in its normal position.
• Get in DIAG Mode #09 to turn the fuel pump on and drain the fuel tank inside the spare tank.
• Get the bike up strait from the sidestand position to finish the draining.
• Some fuel (and dirt) will stay inside the tank, no matter what you do. You'll wipe it out latter with a rag.

Removing the fuel tank

(image)• Lift the tank again, remove the vent hoses (1), the outlet hose (2) and return hose (3). Again, do not use brute force.
• Remove the fuel pump connector (4) and the fuel gauge connector (5).

(image)• Remove the axle screw.
• Remove the fuel tank and place it upside down on a soft plane.

Removing the fuel pump

(image)• Remove the flange of the fuel pump (six screws).
• Remove the fuel pump slowly without damaging the gasket in case it sticks.
• Be careful with the protruding part of the fuel gauge sensor : do not use force, pull it gently and it may come easily, if not unsnap it from the main fuel pump body before extracting it.
• Mop up the remaining fuel and deposits inside the tank with a cloth.

Cleaning the fuel tank



Lots of rust, but especially a lot of sticking paraffin deposits left by the decomposition of the fuel
1 & 2 - How it looks after an initial cleaning with a cloth soaked with engine cleaner fluid.
3 - Closeup near the location of the fuel pump.

Cleaning the fuel tank

There are many different techniques to clean a fuel tank : rust remover fluid, electrolysis, hand scrubbing, etc.

Personally I did not intend to spend my life on it and the rust deposit was not very thick. So I made a first cleaning attempt to see what result could give a mixture of water + soda + various scrap. The result being satisfactory, I did not go beyond that simple process.

I prepared a mixture of about 5 liters of tap water in which I poured to saturation household soda crystals (white powder for domestic use, this is of course not caustic soda). The advantage of using washing soda is that it is not toxic / harmfull, and in addition it is very economical.


1 - Some scrap, more effective than the traditional gravel because it is more dense and has sharper angles. Don't fill the bucket or you'll be sorry !
2 - Pour the mixture and the scrap inside the fuel tank.
3 - The fuel pump hole is sealed with a thick, sturdy plastic round held by the flange installed upside-down.
Hold the fuel tank and shake it vigorously in all directions for a while - fifteen minutes were enough for my arms. It actually depends on the thickness of the rust deposit.


Same locations as above / before.


The result is quite satisfactory, almost all the rust is gone. Drain the tank and rinse it two times with tap water. Remove extra water inside the tank with a rag. To dry the tank, I left it in broad sunlight a good part of the afternoon with the cap left open to allow air flow to pass through it. Finally I used a compressed air blower to dry every corner inside. Acetone may also be used to dry the inside of the tank as it absorbs water.

Cleaning the fuel pump


Disassembling the fuel pump is not very hard, all parts are clipped. First disconnect the two electrical connectors.


1 - Disassembly of the fuel pump is under way, all parts are very dirty and require a good cleaning ! Plastic parts are easy to clean, use an old toothbrush and a cleanser like White Spirit, dry with an air blower.
2 - The motor of the pump is covered with rust, dirt & corrosion. The bottom filter is in a pitiful state.
3 - The motor of the pump is now in better shape. To clean the bottom filter I let it soak overnight in a glass of vinegar then I brushed it, rinsed it with water and then I dried with the air blower.
4 - The main seal and the outlet O-ring. Remove both with care then clean them and the groove. Check the condition of the main seal, if any damage is present replace it. Be aware that the section of the seal is asymmetrical, replace it on the correct side.

The fuel gauge sensor


1 - The sensor track can be covered with waxy deposit. In this case, it will not work, just as if it was disconnected : the fuel gauge indicator on the instrument panel will flash. Test it with an ohm-meter, clean the track with an electrical contact cleaner if required.
2 - Details of the "push & slide" thingy to clip the sensor on the pump assembly : .
3 - The sensor in place, without the float arm.



1 - Reassembly is on its way, the motor is in place.
2 - The bottom filter is replaced on the motor, it is in better condition now !
3 - The fuel pump assembly is almost complete.
4 - Wires routing detail.
The fuel pump assembly is then replaced inside the fuel tank. Clean mating surface. The pump assembly goes more easily through the hole. Put the flange in place (only one orientation is possible as it is asymmetric) then tighten the screws crosswise and gradually (imperative).

Cleaning the fuel tank cap

While you're at it, remove & clean the cap :
• Disassemble completely.
• Take notice of the location of small parts during disassembly, especially the steel ball and the tiny locking finger !
• Do not mix the four springs of the closure support and the single latch spring.
• Clean / deoxidise all the parts, lubricate the moving parts.
• Clean the rubber gasket with soapy water.
• Then reassemble.

1 - Location of the steel ball.
2 - Locking finger and its location.

All done

Replace the cap, replace the fuel tank on the bike, replace the hoses and the connectors, check that you don't get extra parts left, fill the fuel tank and go for a ride...

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