If the motorcycle has been stored in a parking lot without a roof to protect it from rain, the inside of the fuel tank will get rust within a few years, and depending on the condition, even if you think you've stored it well, it will rust sooner than expected.
Removing such rust is a must, but before removing the rust, it is more essential to thoroughly remove the dust and the old dirty gasoline membranes from the inside of the fuel tank.
High-pressure cleaning is the best way to clean the inside of the fuel tank!
After removing the dirt in the fuel tank with a neutral detergent or a commercial degreasing detergent, pour tap water into the fuel tank and insert an air gun with a long nozzle to blow air thoroughly the inside of the fuel tank. In other words, it makes to gargles the inside of the fuel tank. Then let's bounce back the water that is gushing out with a transparent umbrella.
The air gun that reaches to the bottom of the fuel tank is an effective item!
Dirt and rust in fuel tanks often accumulate in the grooves of the tank's welds (seam welding lines). If there is a buildup of dirt, the rust hiding underneath will not react to the rust removal chemicals unless removing that dirt. That's why it's so important to clean the inside of the fuel tank before removing rust.
Replacing the nozzle of a commercial high-pressure wash machine with an optional "tapered nozzle" (called an "underlance") workability will improve. If you don't have a high-pressure wash machine, you can make a jet pressure like a high-pressure wash machine by drilling a hole 50mm before the end of the water hose and inserting the nozzle of an air gun.
You can visually inspect every part with a fiberscope!
The fiberscope that is possible to buy at the tool shop is handy for peering inside through the plug holes to see the carbon buildup on the piston heads, but here you can get a good look at the dirt in the fuel tank. Old altered gasoline sludge has accumulated in the grooves at the seam welding lines.
You can scrape off the dirt in the area that you can see with a bundle of "Annealing Wires".
The annealing wires are often used to tie the pipes of scaffolding at construction sites and exterior wall painting sites. The annealing wires are characterized by its soft, thick, wire-like shape. They can be purchased at home improvement stores. It's easy to use the double-folded annealing wire, and it's good to polish the dirt just below the tank cap with the tip of the bundled annealing wire.
Point 2: If the rust is not exposed, the rust removal chemical will not react.
Point 3: High-pressure cleaning is the most effective way to remove dirt.
The inside of a motorcycle's fuel tank that had been left unattended for a while is often in a surprisingly bad condition. If gasoline is left in the fuel tank, gasoline degrade and become tar-like or varnished. In such a situation, the removal of the dirt becomes a difficult task before the rust removal work.
Some amateur mechanics may have experienced that the inside of the fuel tank didn't clean up even putting in rust removal chemicals after draining the rotten and smelly gasoline. Even with the use of high-performance rust removal chemicals, you'll never get the results you want unless you clean the rotting gasoline dirt in the fuel tank.
There are many cases that the cause of overflow from the carburetor is simply the dirt in the fuel tank rather than rust. Even in such a situation, the method of cleaning the inside of the fuel tank described here will be very useful.
2. Set the lever in the OFF position if the fuel cock is still installed.
3. Put a plug on the mounting part of the fuel cock if no fuel cock.
4. Put about 50cc of neutral detergent such as kitchen detergent, and pour about 60 degrees Celsius hot water into the fuel tank until half of the tank’s capacity (boil water with a kettle and adjust the temperature).
5. Close the tank cap and shake the fuel tank well.
6. After shaking the fuel tank, pour more lukewarm water until the brim of the fuel tank, and close the fuel cap. Wrap the tank with an unwanted blanket to prevent lukewarm water from getting cold and wait for 24 hours.
It is a good idea to dissolve the dirt in the fuel tank with lukewarm water of neutral detergent as described above, and then start the work described in the photo.
If simply removing dirt from the inside of the fuel tank, the inside of the fuel tank will be clean with this work. If finished rinsing with tap water, remove the fuel cock or plug and the tank cap, and dry the inside of the fuel tank under the sun or with warm air from a hairdryer. You can also keep it in the trunk or cargo area of your car with the tank cap and fuel cock removed and wait for it to dry (if there is no smell).
If the inside wall of the fuel tank still has rust after the work is done, continue the treatment process with the high-performance fuel tank rust remover chemical. After the fuel tank is washed, it's time to have fun using this one!