Do you know that the airplane cap, a flat fuel tank filler port that has often been adopted to on-road sports, has a drain function to discharge spilled gasoline on refueling and rainwater?
If the drain hose is clogged, it may cause troubles such as rusting due to accumulated water inside the tank. We would like to check the hose if it can drain the water or not before it causes serious damage.
1. Drain function is required because of an airplane tank cap.
2. Rainwater flows into the tank due to corrosion of the drain pipe or bending of the drain hose!
3. Remove the tank cap, and check the function and condition of the drain hose.
1. Drain function is required because of an airplane tank cap.
An airplane tank cap makes the fuel filler port position lower instead of being flat at the top surface of the tank. The drain hose is important in order to prevent accumulated water around the cap from entering water to the tank. The tank in the above photo has already rusted around the filler port.
The fuel tank cap has a vent function that balances both pressures inside and outside of the tank while not letting the gasoline leak out. That's why all motorcycle tank caps have a small air vent.
Aside from this, the airplane tank cap, which the tank surface and tank cap are designed flat, has a drain hose. The filler port of airplane tank cap is placed one level lower than the tank top surface in order to make the upper surface of the tank flat. In addition, there is a drain port around the filler port to drain spilled gasoline and rainwater out from the tank. The drain hose penetrates inside of the tank and is open to the atmosphere around the back of the step plate.
・The fuel tank cap has a small air vent.
・The airplane cap has also a drain hose.
・The air vent and the drain hose discharge rainwater and spilled gasoline.
2. Rainwater flows into the tank due to corrosion of the drain pipe or bending of the drain hose!
DUCATI fuel cap can be removed with the fuel cap base. The rubber made drain hose is connected with a metal pipe welded to the bottom of the tank.
There is no problem if the indispensable drain hose for the airplane tank penetrates from the drain port around the filler port to the outlet at the bottom of the vehicle body. However, if this hose is clogged up, it will cause serious troubles. In case of the model connected the hose to the rear part of the fuel tank, there was a trouble that hose was crushed when the seat was attached and detached, and water could not be drained. Then the water with no place to go would goes back up the hose to the cap and dives into the fuel tank.
There was also a trouble that rainwater and collected sands around the filler port became a mud dumpling and was clogged the drain pipe. Due to the malfunction of the drain hose, the accumulated rainwater can only enter the fuel tank. The accumulated water in the tank causes rust so it can be a very serious effect.
・Clogged drain pipe could cause water to pour back into the fuel tank.
・Rainwater into the tank could cause rust and serious troubles.
3. Remove the tank cap, and check the function and condition of the drain hose.
The tank cap bolts are detached using a highly accurate wrench so as not to strip the bolt head. Some bolts may be dummy depending on the model.
To check the function of the drain hose, pour water around the tank cap, and check the water flows out from the hose at the bottom of the vehicle. If water does not come out, you should use a waste cloth to suck off the collected water around the filler port, and then remove the hexagon head cap bolt around the cap by a hexagon wrench. If the cap is removed, there is the drain port on the outside of the filler port.
If you have an air compressor, you can remove some dust in the hose that causes clogging by blowing out the air from the drain port. If the air doesn't go through, remove the drain hose, blow air to both metal pipes inside the tank and a rubber hose outside the tank to check which is clogged. In case the rubber hose outside the tank is clogged, crushed, or broken, it is safer to replace to a new one.
▲ In this model, the hole at the top of the filler port is the drain port to the hose. Since the drain port is lower than the edge of the filler port opening, spilled gasoline during refueling and rainwater is discharged outside from this port through the pipe inside the tank.
On the other hand, it is more troublesome if clogging occurs in the metal pipe in the tank. To avoid this, it is better to check the area around the filler port when refueling in case of a motorcycle with an airplane tank cap.
Even though you did not ride your motorcycle in a rainy weather but if the back of the cap is wet, it is also better to check the condition of the drain hose.
・Drain hose check is performed by pouring water to the tank cap.
・In case of small clogging, it can be resolved with air blow.
・If a rubber hose has problems, it is safer to replace it to a new one.
The drain hose is an important part for discharging gasoline and rainwater around the filler port.
In case of a motorcycle with an airplane tank cap, check for the clogged and crushed hoses.The major factor of rust on fuel tank is the contaminating water when operating open and close of the cap. The drain hose that discharges rainwater and spilled gasoline is usually not noticeable. But, the owner of the motorcycle with an airplane tank cap should check if it penetrates properly to prevent rust in the tank.
・Fuel tank drain hose is not usually being taken care of, but it is very important.
・It is recommended to check the area around the filling port when refueling on a sunny day.
