Exhaust Pipe Routing for Open Batteries Causes Rust on Old and Outdated Motorcycles

001-3.jpg How to

Lead-acid batteries, which are discharged and recharged by a chemical reaction between lead plates and diluted sulfuric acid, are essential for powering motorcycles and automobiles. Recently, the maintenance-free type is the mainstream, but the open-type is still alive and well, especially in outdated and old motorcycles. Do you know the importance of the exhaust pipe that is always attached to such open-type batteries?

Open-type battery that generates oxygen and hydrogen gas by chemical reaction

02-5.jpg The GPZ400F was introduced in 1983 and became popular for its sleek styling with half cowl like its big brothers, 1100F, 750F and 550F, and the engine that produced 54 horsepower even though it was air-cooled and had 2 valves. The battery is naturally an open-type, YB10L-A2 (for GS Yuasa).

03-5.jpg The tachometer is equipped with a voltmeter and the LCD monitor on the fuel tank has a warning display that flashes when the electrolyte level drops. This is a unique feature of an open-type battery as the water in the electrolyte is reduced by repeated charging and discharging.

04-5.jpg The pink part is a liquid volume sensor that is installed by replacing the cap of one of the cells containing electrolyte. The LCD monitor blinks when the electrolyte stops touching the electrode at the tip. When the liquid level is just below the lower level, the electrode may be exposed and blink due to the posture change caused by acceleration and deceleration.

Prior to the 1980s, the only way to mount a battery was vertically to prevent leaks, as the only way to mount a battery was with three caps on a 6V motorcycles and six caps on a 12V motorcycles. However, with the introduction of sealed, maintenance-free batteries, it is now possible to mount the batteries in any way, vertically, horizontally or diagonally, and this has undoubtedly increased the degree of freedom for motorcycle manufacturers when developing new models.

There is no difference in the chemical reaction of charging and discharging using an electrode containing lead and an electrolyte of dilute sulfuric acid, whether it is an open-type or a sealed type. However, the sealed type is designed so that the oxygen gas generated during the chemical reaction is absorbed by the electrode plates, while the maintenance-free type, in which the electrolyte is made into a gel or soaked into the separator, has less electrolyte in liquid form, so the electrolyte does not spill no matter how the battery is tilted.

In contrast to such modern batteries, the open-type familiar from old and outdated motorcycles is filled with liquid dilute sulfuric acid inside the battery housing. When charging, the electrolyte undergoes electrolysis, generating oxygen gas from the positive electrode plate and hydrogen gas from the negative electrode plate. This is part of the electrolyte volatilized by the gas generated during charging. When a new battery is replenished before it is installed in the vehicle, small droplets of water will adhere to the electrolyte inlet, but this is part of the electrolyte that has been volatilized by the gases generated during charging.

Even after the battery is installed in the vehicle body, the water content in the electrolyte gradually decreases due to the gas generated when charging the battery with electricity generated by the alternator, so it must be replenished periodically. The exhaust pipe is designed to discharge gases generated during charging and electrolyte when the vehicle is tilted or tipped over.

POINT
  • Point 1: The open-type battery generates gas when it is charged, but the sealed MF battery absorbs the oxygen gas generated by the electrodes and does not release it to the outside.
  • Point 2: Gases and electrolyte droplets generated by open-type batteries are discharged from the exhaust pipe.

The exhaust pipe is important as an escape route for gases and electrolyte from the reaction

05-5.jpg Whether it is an open-type or maintenance-free battery, a new battery can be fully charged by replenishing the battery before use, providing stable performance over a long period of time.

In the case of a 12V battery, six cells are connected together to generate 12V, with each cell generating 2V as a unit, and the piping elbow is placed across the top of each cell to discharge the gas and electrolyte generated in each cell. The piping elbow is placed across the top of each cell and discharges the gas and spilled electrolyte generated in each cell together.

In the case of open-type batteries, gas is produced as a chemical reaction even when the battery is in a normal state of charge. Some of the older regulated rectifiers have a higher charge voltage, which causes more gas to be produced. This also means that the water in the electrolyte evaporates more quickly, so the fluid level must be checked more frequently. If the charging voltage is lower, the gassing is reduced, but it cannot be eliminated because the battery must be charged at a higher voltage than the current voltage.

This is where the exhaust pipe, which is inserted at the end of the elbow, comes into play. This pipe, along with the drain tube of the carburetor, is open to the atmosphere underneath the vehicle and allows the gases produced by the battery to escape. The exhaust pipe is located on the inside of the sight cover, the battery case, the rear wing and in the owner's manual.

Batteries, which store the electricity essential to riding a motorcycle, are at the same time very dangerous and delicate in the age of the open-type battery. As any rider who has ever accidentally come into contact with dilute sulphuric acid will tell you, it can easily puncture clothing and, if it gets on the skin, it can cause burns and skin damage. Even if you want to use this component safely, it generates hydrogen gas and oxygen gas, and there is a possibility of spilling diluted sulfuric acid, which is why it is important to connect the exhaust pipe securely.

POINT
  • Point 1: The diluted sulfuric acid in the battery electrolyte is highly acidic and dangerous, so discharge it from the lower part of the vehicle using an exhaust pipe.
  • Point 2: To prevent the pipe from collapsing in the middle, set the pipe as instructed by the motorcycle manufacturer.

Depending on how the pipe is threaded, the frame and swingarm can rust.

06-5.jpg This is an example of the exhaust pipe being crushed by the battery case and split in the middle, causing the upper mount of the rear suspension to rust. This is one of the strongest parts of the frame and should not be routed like this. Of course, this is not the placement specified by the manufacturer, but it is due to the owner's mistake.

07-4.jpg The battery case of this GPZ400F is unique. The exhaust pipe is not directly inserted into the piping elbow of the battery but into the flange of the battery case like a drain. The rust on the frame around this area was caused by the electrolyte splash.

08-4.jpg The piping elbow of the battery and the flange of the battery case is offset, causing the short pipe to bend like a crank. If it is crushed in this area, the gas and electrolyte droplets will leak directly under the piping elbow before flowing to the exhaust pipe under the battery case, so be careful not to force it in.

09-1.jpg When using a handy pipe as an exhaust pipe, cut a slit with a cutter near where it inserts into the piping elbow. The gas and electrolytic solution generated is usually discharged through the pipe, and the purpose of the slit is to discharge it only when the pipe is crushed or clogged for some reason, so it is useless near the outlet.

A common problem with exhaust pipe is collapsed pipe. If the pipe is crushed by other parts on the way from the battery case to the lower part of the body through the inside of the side cover and along the pipe guide, the gas and electrolyte in the pipe will not flow and will accumulate. However, there are many cases where the exhaust pipe is placed in a place where it is easy to pass and the side cover is set, but the pipe is crushed inside the cover. There are many cases where the pipe was crushed inside the cover.

The battery manufacturers use thicker tubes to prevent them from crushing easily, but some riders intentionally replace them with thinner, softer tubes because they are too hard to handle.

If the pipe collapses in the middle of the pipe, there is no escape for the gas that is discharged from the piping elbow, and hydrogen gas can also pose a risk of explosion. This is why battery manufacturers have slits or small holes in one side of the exhaust pipe to allow the pressure to build up if the pipe collapses in the middle. If you use a generic tube for your exhaust pipe, make sure you cut a slit just below where you insert it into the elbow.

However, having the slit near the piping elbow means that the gas exit is near the battery case or frame, and if dilute sulfuric acid from the electrolytic solution adheres, the paint will peel and the frame will corrode. The slit is only an emergency relief release valve, and the original idea is to pass through a route that does not collapse the pipe so that it can be discharged from the bottom of the exhaust pipe.

In addition, there are people who cut the exhaust pipe that hangs down from the bottom of the body of the motorcycle when looking at it from the side, and it is not cool. If the pipe outlet is close to the swing arm or frame, the discharged electrolyte will damage the paint.So, aside from style, it's best to keep the exhaust pipe outlet down to the bottom of the frame.

Although open-type batteries require more work than high performance maintenance-free or modern lithium-ion batteries, such as regular water and power replenishment, it is also important to take care of the exhaust pipe to maximize performance.

POINT
  • Point 1: Make a slit in the upper part of the pipe so that the gas can be discharged even if the exhaust pipe collapses in the middle.
  • Point 2: Install the exhaust pipe without cutting it in the middle to avoid damaging the paint on the swingarm and frame.

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See Accessories for KAWASAKI GPz400F/F2

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