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Harley M8 Breather Bypass: What You Need to Know for Optimal Performance

harley m8 breather bypass

One aspect of maintenance that you may not have considered is the breather system. The breather system is responsible for venting excess air pressure and oil vapor from the engine. However, the stock breather system on the Milwaukee-Eight (M8) engine has been known to cause issues with excess oil consumption and carbon buildup.

Luckily, there is always a solution to a problem: specifically the Harley M8 breather bypass. This modification allows you to vent excess air pressure and oil vapor into a catch can or the oil pan, reducing carbon buildup in the combustion chamber and prolonging the life of your engine. Not only that, but a breather bypass can also improve the performance of your Harley by reducing drag on the engine caused by excess pressure. If you’re looking to improve the longevity and performance of your Harley, a breather bypass may be just the modification you need.

TLDR Summary

If you’re looking to improve the performance and longevity of your Harley Davidson M8 engine, a breather bypass modification might be just what you need. This modification can help reduce oil consumption, prevent carbon buildup in the combustion chamber, and keep your air cleaner free of oil.

The Harley breather bypass mod works by venting crankcase pressure and blowby into a catch can or the oil pan. This helps to reduce the amount of oil vapor that the engine produces, which can be a common issue with the Milwaukee-8 engine.

To create a bypass breather, you’ll need to remove the air cleaner and filter and then reroute the breather hoses off the head bolts. You can then run a new line down the back of the backing plate, out the hole, down the back of the engine, and under the oil tank. You can also add an in-line filter to help prevent any oil from entering the catch can or oil pan.

Overall, the Harley breather bypass mod is a simple way to improve the performance and longevity of your M8 engine. With just a few modifications, you can reduce oil consumption, prevent carbon buildup, and keep your air cleaner free of oil.

What is a Harley M8 Breather Bypass?

If you own a Harley Davidson M8 engine, you might have heard about the Harley M8 breather bypass. This modification is designed to vent the crankcase pressure and blowby into a catch can or the oil pan, which can help reduce carbon buildup in the combustion chamber.

The main issue with the breather design on the Milwaukee-8 is that, in some cases, these engines produce more oil vapor than usual. This can lead to oil consumption and carbon buildup in the engine, which can affect its performance.

By installing a breather bypass, you can eliminate these issues and improve the overall performance of your engine. The bypass redirects the crankcase pressure and blowby away from the intake and exhaust systems, which can help reduce oil consumption and carbon buildup.

The Harley M8 breather bypass is a relatively simple modification that can be done in a few hours with basic tools. The process involves removing the air cleaner and filter, installing the catch can or oil pan, and rerouting the breather hoses.

Overall, the Harley M8 breather bypass is a great way to improve the performance and longevity of your engine. It is a popular modification among Harley enthusiasts and can provide noticeable results. If you are experiencing issues with oil consumption or carbon buildup, consider installing a breather bypass to help solve these problems.

Why Do You Need a Harley M8 Breather Bypass?

If you own a Harley Davidson Milwaukee-8, you may want to consider installing a breather bypass. Here are a few reasons why:

  • Reduce Carbon Buildup: The breather bypass will minimize the carbon buildup on the pistons, rings, and valves; this will cause less wear on the engine, resulting in longer engine life.
  • Better Performance: A Harley with a breather bypass will also perform better than one without. You’ll have much less carbon buildup on the pistons, rings, and valves, which means the engine can run more efficiently.
  • Increased Engine Life: Running a breather bypass will significantly increase the life of your Milwaukee-8. You won’t have to worry too much about carbon buildup causing damage to the engine, and you’ll save money in the long run.
  • Prevent Blowby: If you’ve ever overfilled your oil reservoir, you know how dramatic blowby can be. A bypass system directs the vapors down and toward the back of the bike, either to a catch can or just to the atmosphere.
  • Improve Power: By reducing the amount of carbon buildup in the engine, a breather bypass can improve the power of your Harley. You’ll notice a difference in acceleration, especially at higher speeds.

Overall, a Harley M8 breather bypass is a simple way to improve the performance and longevity of your Harley. It’s a small price to pay that can pay off big in the long run.

How Does a Harley M8 Breather Bypass Work?

If you’re wondering how a Harley M8 breather bypass works, you’re in the right place. The breather bypass is a modification that can be made to your Harley Davidson motorcycle to help improve its performance and longevity. Here’s how it works.

When your engine is running, it creates pressure inside the crankcase. This pressure can cause oil vapors to be pushed out of the engine and into the air cleaner. Over time, this can cause carbon buildup on the pistons, rings, and valves, which can lead to wear and tear on the engine and reduced performance.

By installing a breather bypass, you can redirect these oil vapors away from the engine and into a catch can or oil pan. This helps to reduce carbon buildup in the combustion chamber and can lead to better engine performance and longer engine life.

To install a breather bypass, you’ll need to remove the air cleaner and filter from the cleaner assembly. Depending on the brand, type, or style of air cleaner you have, you may also need to remove the back plate. Once you have access to the breather hoses, you can reroute them to the catch can or oil pan.

It’s important to note that the Milwaukee-8 engine can produce more oil vapor than usual, so it’s especially important to install a breather bypass if you have this type of engine. Additionally, it’s important to check the catch can or oil pan regularly and empty it as needed to prevent overflow.

Overall, a breather bypass can be a simple and effective way to improve your Harley’s performance and longevity. By redirecting oil vapors away from the engine, you can help reduce carbon buildup and keep your engine running smoothly.

Installing a Harley M8 Breather Bypass

If you’re looking to improve your Harley Davidson M8 engine, installing a breather bypass can help. The process of installing a breather bypass is relatively straightforward and can be done with just a few tools. Here’s a step-by-step guide to installing a Harley M8 breather bypass on your motorcycle.

Step 1: Remove the Stock Breather Bolts

The first step in installing a Harley M8 breather bypass is to remove the stock breather bolts. These bolts are located on the top of the engine and are used to vent gases from the crankcase. To remove the bolts, use a socket wrench to loosen them and then remove them by hand.

Step 2: Install the M8 Breather Bolts

Once the stock breather bolts have been removed, it’s time to install the M8 breather bolts. These bolts are designed to allow fresh air to enter the engine while preventing oil from escaping. To install the M8 breather bolts, simply screw them into the engine using a socket wrench.

Step 3: Install the External Breather Kit

With the M8 breather bolts in place, it’s time to install the external breather kit. This kit includes a hose and a filter that will allow the engine to vent gases to the outside of the motorcycle. To install the external breather kit, attach the hose to the breather bolts and then attach the filter to the end of the hose.

Step 4: Install the Harley M8 Catch Can (Optional)

For those who want to further improve the performance of their Harley-Davidson M8 engine, installing a catch can be a great option. A catch can is designed to capture any excess oil that may escape from the engine and prevent it from entering the air intake. To install the Harley M8 catch can, simply attach it to the breather hose using a hose clamp.

By following these steps, you can easily install a Harley M8 breather bypass on your motorcycle. This will allow your engine to breathe more easily and improve its overall performance.

Benefits of a Harley M8 Breather Bypass

If you own a Harley M8, you might have heard of the term “breather bypass.” It’s a modification that can have significant benefits for your motorcycle’s engine. Below are some benefits of a Harley M8 breather bypass:

Reduced Oil Consumption

One of the biggest and most significant benefits of a Harley M8 breather bypass is that it can significantly reduce your engine’s oil consumption. If you’ve been burning oil through the breathers, you’ll notice that your oil level stays nice and full after switching to a catch can setup. This means you’ll save money on oil changes and have a cleaner engine overall.

Increased Engine Life

The breather bypass mod can significantly increase the life of your Milwaukee-8 engine. You’ll have much less carbon buildup on the pistons, rings, and valves. This means your engine will run smoother and more efficiently, and you’ll save money on repairs in the long run.

Improved Performance

A Harley M8 breather bypass can also improve your motorcycle’s performance. By reducing the amount of oil that gets into the air cleaner and the combustion chamber, you’ll have a cleaner and more efficient engine. This means you’ll have better throttle response, more power, and better fuel economy.

Easy Installation

Installing a Harley M8 breather bypass is relatively easy and can be done with basic tools. You can purchase a kit that has everything you need to install the bypass, including banjo bolts or hose barbs, hose, clamps, and a breather drool cup (optional). With a bit of time and effort, you can have a breather bypass installed and start enjoying the benefits of a cleaner and more efficient engine.

In summary, a Harley M8 breather bypass is an excellent modification that can have significant benefits for your motorcycle’s engine. By reducing oil consumption, increasing engine life, improving performance, and being easy to install, it’s a modification that any Harley M8 owner should consider.

Maintenance and Cleaning

Keeping your Harley M8 breather bypass system in good condition is essential for the longevity of your engine. Regular maintenance and cleaning will help prevent oil leaks and ensure that your engine runs smoothly. Below are our tips and tricks on how to maintain and clean your breather bypass system:

  • Check your catch can regularly: Your catch can should be checked and cleaned regularly to ensure that it is functioning properly. If you notice any oil accumulation in the catch can, it is time to clean it out. Simply remove the can, empty the contents, and clean it with soap and water.
  • Inspect your hoses: Make sure that your hoses are in top condition and free from cracks or damage. If you notice any issues with your hoses, it is important to replace them immediately to prevent any oil leaks.
  • Clean your air filter: Your air filter should be cleaned or replaced regularly to ensure that your engine is getting enough air. A dirty air filter can cause your engine to run poorly and may lead to oil leaks.
  • Use high-quality oil: Using high-quality oil is very important for the longevity of your engine. Make sure that you are using the recommended oil for your bike and that it is changed regularly.
  • Check your oil level: This goes without saying, as it is important to ensure that your engine is not running low on oil. If you notice that your oil level is low, it is important to add more oil immediately.

If you make sure you do all of the above, you can help ensure that your Harley M8 breather bypass system is functioning properly and that your engine is running smoothly. 

Other Considerations

When it comes to the Harley M8 breather bypass, there are a few other considerations that you should keep in mind. One of the most important is the Twin Cam crankcase breather. This is a crucial component of your bike’s engine that helps to reduce pressure buildup and prevent oil leaks.

If you are planning to install a breather bypass on your Harley M8, it is very important to make sure that your Twin Cam crankcase breather is working properly. This will help to ensure that your engine runs smoothly and that you don’t experience any oil leaks or other issues.

To check your Twin Cam crankcase breather, you should remove the air cleaner cover and inspect the breather bolts for any signs of damage or wear. If you notice any issues, it is important to replace the breather bolts as soon as possible.

In addition to checking your Twin Cam crankcase breather, you should also make sure that you’re using the correct oil for your Harley M8. Using the wrong oil can cause some big issues for your engine, so make sure you choose the right oil for your bike.

When selecting oil for your Harley M8, you should look for oil that is specifically designed for air-cooled engines. This type of oil is formulated to withstand high temperatures and provide superior protection against wear and tear.

Overall, if you are planning to install a breather bypass on your Harley M8, it is important to take the time to check your Twin Cam crankcase breather and choose the right type of oil for your bike. By doing so, you can help to ensure that your engine runs smoothly and that you get the most out of your Harley M8.

Wrap Up!

In conclusion, bypassing the breather on your Harley M8 engine can have several benefits. It can reduce carbon buildup and improve engine performance, leading to longer engine life. There are several ways to create a bypass breather, including drilling a hole in the air cleaner’s back plate or using a custom breathing system.

When creating a bypass breather, it is important to follow the proper steps and use the right tools. Removing the air cleaner cover and filter is usually the first step, but it may vary depending on the brand or type of air cleaner you have. Make sure to consult the manufacturer’s instructions or go to a proper mechanic if you are unsure.

Lastly, creating a bypass breather may not be legal in all areas. Make sure to check your local laws and regulations, as you don’t want to do anything illegal and get in trouble later on.

Overall, if you are looking to improve the performance and longevity of your Harley M8 engine, creating a bypass breather may be a worthwhile investment. With the tools and know-how, you can create a custom breathing system that will help your engine run smoother and last longer.