How To Bleed Motorcycle Brakes?

Bleeding your motorcycle brakes is an essential part of maintenance. The procedure entails removing air bubbles from the braking system and replacing the brake fluid. Air is a compressible gas, and it compresses when it enters the brake lines of your motorcycle. The pedal or lever moves, but the piston does not. As a result, the brakes lose their braking power.

Bleeding is not as difficult a task as one thinks it to be but needs to be done carefully to get it right. It is recommended that this be done every two years. Are you planning to bleed your motorcycle brakes and wondering where to begin? Then you have arrived at the right place.

In this guide, we will explain the process in detail and answer all of your questions. Let’s get started, shall we?

Why Do You Need to Bleed Your Motorcycle Brakes?

Before we get into the steps of bleeding the motorcycle brakes, let’s understand the reasons you need to do so. Take a look:

  1. You want to perform regular maintenance of the motorcycle by flushing out the brake fluid that has become dark or discolored lately. Brake fluid should be clean and clear.
  2. You replaced your motorcycle’s braking components that introduced air bubbles into the brake lines. This reduces your braking power.
  3. Your motorcycle has a poor brake lever or brake pedal feel and must bleed the brakes to fix it.

Preparing the Motorcycle For Bleeding

You must first prepare your motorcycle for a successful brake bleeding. Before you start bleeding the motorcycle, there are a few things you should do:

Cover it up

Brake fluids are corrosive in nature and can ruin the paint of your bike. This is why it is recommended to throw a sheet over the motorcycle to protect the painted surfaces. You can cover the parts near the bleeder valve and the handlebar with small rags.

Choose the right brake fluid

Choosing the right brake fluid is imperative for the health and maintenance of your motorcycle. You can find the DOT (Department of Transportation) preferred type of brake fluid mentioned on the master cylinder, also known as the brake fluid reservoir of your motorcycle. There are three types of brake fluids – DOT 3, 4, and 5.

The higher rating of DOT 4 means it has a higher boiling point than DOT 3. DOT 5, on the other hand, is a silicone-based fluid that doesn’t absorb moisture. It has a higher boiling point. It can be used as a replacement for DOT 3 and 4 but should never be mixed with either of them.

Use brake fluid from a sealed container

Brake fluid is hygroscopic which means it absorbs moisture as soon as it is exposed to air. Therefore, make sure you use the fluid from a sealed container. The trick here to follow is to buy small containers that you can use up in one go.

Pro tip: Always use fresh brake fluid from an unopened bottle that has no water/moisture content.

Check the fluid level regularly

As brakes are a sealed system of a motorcycle, you need to be alert all the time. If you are losing brake fluid regularly, it could be something more than what a simple bleeding process can fix. If the fluid level begins to fall, stop adding more. It is possible that you will need to hire a professional for this.

How to Bleed Your Motorcycle Brakes?

Here’s how you can start bleeding your motorcycle brakes step by step:

Clean Up Your Bike

Before you begin the bleeding process, we recommend that you clean the brake reservoir, calipers, and brake lines with a towel or cloth once again. Make sure you check the condition of the diaphragm. If it is damaged or worn out, it’s best to get it replaced as soon as possible. 

Remove the Dust Cover from the Bleeder

Carefully remove the cap or dust cover from the bleeder bolt and install a clear vinyl hose on the caliper. This cap is usually made of rubber and prevents harmful foreign objects like muck, salt, and dust from getting into the bleeder threads. Now, run the hose to an empty container or bottle, so that brake fluid doesn’t get spilled everywhere.

Pro tip: Fill the container/bottle with a small amount of brake fluid beforehand. It should be sufficient to immerse the vinyl hose in the fluid. This will keep air from being sucked into the brake system while it is bleeding.

Top off the Master Cylinder with Brake Fluid

Remove the cap from the master cylinder reservoir and refill it with clear and clean brake fluid if necessary. If you don’t do this, the air is most likely to get sucked into the brake lines, and the bleeding process will take longer than usual. When finished, put the cap back on but do not tighten it. Some people prefer to remove the cap, but this can cause brake fluid to spill out of the master cylinder, destroying the paint.

Start bleeding at the farthest point from the master cylinder

Begin bleeding your motorcycle brakes as far away from the master cylinder as possible. We recommend this because it can help you drive out the moist air quickly while also requiring less pumping. This method is useful if you have a lot of air in your brake lines, which is common after installing new braided stainless steel lines on your motorcycle. For bikes with dual-disc front brakes, beginning with the left front caliper.

Build Pressure in the Brake System

Now, it’s time to build pressure to start the bleeding process. For this, you need to pump the brake lever multiple times rapidly. You need to build enough pressure for air bubbles and fluid to come out of the hose. 

Open up the Bleeder Valve

For this step, you will need a wrench, the size of which will depend on the bleeder bolt of your motorcycle. Once you build enough pressure, open the bleeder valve, also known as the bleeder nipple using the wrench. Please note that you will have to hold the brake lever and keep it pushed against the handlebar until the bleeder nipple is open. Don’t release the lever until you have closed the valve. Now, you will see air bubbles and fluid rush through the hose into the draining container.

Add more fluid to the master cylinder

Next, shut the bleeder valve and release the brake lever. Repeat this process as needed until the lever feels firmer and there are fewer air bubbles in the hose. You can always add more fluid to the master cylinder for an extended bleeding process. Make sure the brake fluid reservoir doesn’t go empty during this.

Once you are done, you can move on to the other caliper and repeat the aforementioned steps. This is for the bikes with dual disc front ends and top bleeders.

Things to Keep in Mind While Bleeding a Motorcycle

Now that you have an idea of how to bleed your motorcycle brakes, here are a few things you need to keep in mind during the process:

To swap the fluid, perform an extended bleed

While performing the bleed, use plenty of brake fluid. Bleed as much as you can while keeping the master cylinder from drying out. When the fluid level begins to fall, top it off with more to perform an extended bleed. The goal should be to remove all of the air from the brake system.

If you can’t get the pressure, try a gravity bleed

Sometimes a normal bleeding process is unable to build enough pressure on the motorcycle. By increasing the pressure in the brake lines, gravity bleeding can assist you in releasing air bubbles. It is only effective when the caliper is lower than the master cylinder. To accomplish this, raise your motorcycle above the ground and follow the steps outlined above.

Make sure the bleeder is facing up

If the hose isn’t facing upwards, the bleeding process won’t work. Air bubbles travel upwards, and fluid travels downwards. Loosen the caliper and rotate it until the bleed port is facing down.

How To Bleed Your Motorcycle With a Vacuum Pump?

Here’s another method to bleed your motorcycle brakes. All you need to do is follow the given steps:

  1. Purchase a brake bleeding kit that will include a hand vacuum pump, a couple of hoses, a reservoir bottle, and adapters that will fit on the caliper’s bleeder valve. You can buy it on Amazon.
  2. Open the brake fluid reservoir and remove the cap and diaphragm. Fill it with brake fluid to the top.
  3. Now, pump the brake lever gently, and you will notice the fluid level dropping down. Keep doing this until you feel resistance on the brake lever, and then top the fluid again.
  4. Take the rubber cap off the bleeder nipple, open it with a wrench and then tighten it with your hand.
  5. Attach a clear hose to the adapter that fits the bleeder valve. Then run it into a reservoir bottle. Attach another hose to the bottle and connect the hose’s other end to the vacuum pump.
  6. Now connect the open end of this arrangement to the bleeder nipple and make sure it hangs downwards.
  7. Take the vacuum pump and pump it 10 times. If your vacuum pump gauge displays a consistent reading, this means that everything is properly connected.
  8. Next, open the bleeder valve and keep pumping the pressure. You will see the fluid coming out of the hose. Try to maintain the mercury at 21 inches to keep the fluid coming out at a steady pace.
  9. If the reservoir is not yet empty, air will be sucked into the system. As soon as the reservoir begins to drain, close the bleeder bolt.
  10. Repeat the process until all of the air has been sucked out of the system. If you check the brake levers at this point, you will notice some resistance. Once you are satisfied, use a wrench to tighten the bleeder valve.

How to Bleed Your Motorcycle Brakes with ABS?

Many bike owners believe that bleeding ABS motorcycle brakes is a difficult task. If you agree, we have some good news for you. The process of bleeding motorcycle brakes on vehicles equipped with ABS in most bikes is nearly identical to that of vehicles without it.

You might need an ABS pump for the process. If you are not confident about doing it yourself, we suggest you hire a professional technician or send your motorcycle to the shop. Trust us, it’s a better option than DIY-ing brake bleeding and making a mistake that cannot be reversed.

Frequently Asked Questions (FAQs)

Q. How often should I bleed motorcycle brakes?

You should change your motorcycle fluid once every two years. This is because brake fluid absorbs moisture and degrades over time as a result of the heat generated in the braking system.

Q. What will happen if I don’t change my brake fluid?

If you do not change your brake fluid, it will cause moisture contamination and debris buildup in your brake reservoir. It can result in poor braking performance, which can be dangerous over time.

Q. Do I need extra help while bleeding the motorcycle brakes?

It’s a wise decision to seek assistance when bleeding your motorcycle brakes, especially if it’s your first time. You may need to have someone hold the lever while you open the bleeder valve.

Conclusion

To summarise, we hope we were able to adequately explain the process to you. It is critical to be patient during the brake bleeding process and to be prepared to not get the desired results all at once. Prepare your bike beforehand to protect it from getting spoiled by the brake fluid.

Make sure you have enough time to perform the bleed and, if necessary, seek assistance. It does not have to be a one-person job. You can also get it done by a trained mechanic and then do it yourself the next time the brake fluid needs to be changed.

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