There are many "sliding parts" that rub against each other in the mechanism of a motorcycle, and among these parts, the front and rear brake parts are the most important security parts, and these parts also have many sliding points. Whether it's a drum brake or a disc brake, moisture is the natural enemy of the mechanism. In this article, we disassembled and maintained the master cylinder of a disc brake model that had a strange lever touch (i.e., a spongy feel) when the brake lever was actuated, and did not feel like it had a firm grip.
Rubber parts x metal parts = rubber grease is the correct answer.
This rubber grease is effective in reducing friction loss (friction resistance) when used on contact and sliding surfaces between metal and rubber parts. This product is Superzoil's rubber grease which is popular as a rubber grease to reduce sliding resistance. Lack of oiliness will increase the resistance of rubber parts and significantly reduce their operability, but rubber grease is soluble in glycol-based lubricants such as brake fluid, so it can be used safely even during brake maintenance.
I was able to grip the lever even in this condition
Years of sitting in a warehouse had turned the brake fluid into what looked like crushed jelly. The little brake fluid that remained in the brake hoses managed to keep the caliper pistons working, so they functioned as brakes, but there was no way to expect them to perform.
Be especially careful when removing and installing the dust boot.
If the dust boot is resilient when you touch it, you can reuse it for the time being. To avoid cutting the boot, let's remove the fixed part of the low-pressure entry and the retaining ring of the boot carefully. If the area around the boot is dirty and not easy to work with, it is good to clean the area around the boot with a small brush in a cup or container while pouring hot water from a pot to warm up the entire part. After removing the boot, remove the circlip that holds the inner piston in place.
The brake fluid inside the master cylinder had also been gelled. The master inners for off-road vehicles and small displacement road models are quite small in size due to the small caliper piston diameter. The brake pistons, which have an integrated cup seal (oil seal), were submerged in hot water and cleaned thoroughly with a neutral detergent and brush before being air blown. After it is dry, it is ready for assembly and restoration.
Check the condition of the fluid level inspection window.
One thing that is often overlooked and requires attention is the master cylinder's viewing window to check the brake fluid level. If it is cracked and fluid is leaking, it must be replaced, but replacement parts are not readily available for current models. There are two ports on the bottom of the reserve tank of the master cylinder, and if the small hole on the front side is clogged with debris, it will be impossible to bleed the air. If it is obviously clogged with dust, dirt, or corrosion, poke it with a needle to secure the ventilation port.
Grease up after complete drying
After removing the inner piston, clean and air blow it, and dry it thoroughly. In addition, use a magnifying glass to check the cup seal edges for damage or partial uneven wear. Let's see if there is any damage or partial uneven wear on the cup seal edge. If there is uneven wear on the cup seal, replace it with a new inner kit and a new cup seal. Apply rubber grease if it is determined to be reusable. When restoring the inner kit to the master cylinder body, let's also inspect the inside of the master body cylinder with a loupe. If there is any dirt, use the edge of a pair of disposable lunch chopsticks to remove the dirt without scratching it.
- Point 1: The condition of the brake master can be judged by the touch of the brake lever.
- Point 2: Parts can be prolonged by periodic disassembly and maintenance, not just overhaul for parts replacement.
- Point 3: If reuse of disassembled parts is assumed, disassembly workability will be improved by using hot water to warm up the parts.
Even if it has been a while since you have pulled out your motorcycle to ride, or if you are happy to say "I have a motorcycle I don't want to ride, come and pick it up at", it can be very difficult to pull out your motorcycle if the front and rear brakes are sticking or dragging. Especially for drum brake models, moisture is a big enemy. A few years in the open air can often cause considerable damage. It is not uncommon for the friction part of the shoe to snap off upon impact when the wheel is removed and the brake panel is pulled out of the hub. I'm sure there are many people who have had this experience. In drum brake shoes, the friction material is baked on with adhesive, and if the aluminum surface of the shoe itself corrodes, the white rust from the aluminum will lift the friction material, often resulting in disappointing results.
What about the disc brakes? If left out in the open, they are more susceptible to damage than drum brakes. However, if the motorcycle is stored in a warehouse or under a roof, not directly exposed to rainwater, and on concrete or wood, it is unlikely to be damaged. There are various know-hows for storing motorcycles, so when storing your important motorcycle, it is better to use various ideas than just covering the motorcycle body.
This time, we practiced maintenance on a brake master for an off-road model that had been neglected for years. Off-road brake calipers are highly resistant to moisture and humidity because they are used on rough roads, in the woods, and sometimes across streams. The calipers on the model we tested this time had plastic caliper pistons, so the pistons did not rust and stick to the caliper body. However, as expected, if the piston seals were damaged, the pistons would stick. Over the years, moisture has caused the caliper side to accumulate crystallized brake fluid in the piston seals and dust seal grooves. This causes the piston to move less. On the master cylinder side, the brakes still worked, but the touch on the lever was not as smooth as it should be. When I removed the reserve tank cap of the brake master, I found that the brake fluid had changed to a kind of agar-like crushed jelly. It looked like crushed jelly or agar. The cause of this brake fluid deterioration is also "moisture". Depending on the balance of temperature and humidity in the storage area, this kind of condition can occur. Even in such a situation, the brake fluid was not completely sticking, so we decided to disassemble and clean it. So I decided to start the work immediately.
Brakes are one of the most important safety parts, and it is the responsibility of the machine owner to take care of them when performing DIY maintenance. However, it has been my experience that if the calipers are not completely seized, it is not a big challenge to maintain them. The important thing is to clean the parts thoroughly and visually inspect them to make sure there are no defects in the functional parts. The important thing is to clean the parts thoroughly and visually inspect them to make sure there are no defects in the functional parts. In the case of the master cylinder itself, make sure that the two ports at the bottom of the reserve tank are not clogged. The portholes on the brake hose side are very small, so if they are clogged or dirty, it will be difficult to bleed the air. If the holes are clogged with sludge from the modified brake fluid, you should be able to restore the airflow by poking it with a very thin needle and blowing air through it.
The extracted inner kit is cleaned with new brake fluid. If the inner kit is very dirty like this one, it is better to submerge it in hot water to break down the dirt, and then rub it with your fingertips or brush it with a small brush (toothbrush, etc.). Use a loupe to check for uneven wear on the seal sliding periphery. In particular, check carefully. If there is uneven wear, the shine will be different from the rest of the circumference, and this can be clearly determined. The chemical that should be used when restoring is rubber grease, which improves the sliding properties of metal and rubber parts. This is the very product that shows high lubricity at the point where the metal surface rubs against rubber, rubber parts, and plastic parts. Spray chemicals that have the same effect are also available, so it is best to use different ones depending on the situation.
