If you’ve decided to upgrade your HD to stage 1, then my hat’s off to you.
Making the decision to soup up your motorcycle is a great way to increase its power, looks, and even resale value. Now, when you’re upgrading your Milwaukee 8, you have to do it properly and logically, which means starting off at stage 1 – airflow.
Airflow is the most important part when it comes to squeezing more power out of your M8. We can inject as much fuel as we want, but we will always be limited by the amount of airflow that’s going to the engine. It doesn’t matter if you’ve got a big bore kit, performance cams, etc. – they won’t work without proper airflow.
I can’t emphasize this enough – getting a high-quality air cleaner for your motorcycle is key, as every part of the engine depends on it, including potential future stage 2, stage 3, and stage 4 mods.
That being said, there are A TON of air cleaners on the market, and it can be tough to pick the right one. To help you out, I’ve put together a list of the best stage 1 air cleaners for Harley Davidson M8 motorcycles.
So, without further ado, let’s get started.
Also Read: The Best Oil for Harley Davidson Twin Cam?
The 5 Best Stage 1 Air Cleaners for Harley Davidson M8
 | 1. K&N Street Metal RK-3956 |
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 | 2. Arlen Ness 90° Monster Sucker |
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 | 3. Vance & Hines Rogue VO2 |
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 | 4. Happy-motor Turbine Filter |
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 | 5. Clarion See-Through Air Cleaner |
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1. K&N Street Metal RK-3956
K&N is one of the most popular brands when it comes to air filters and cold air intakes, so it’s no surprise that they’re no. 1 on our list as well.
The K&N Street Metal air cleaner is big, bad, and beautiful – perfect for a stage 1 mod. It’s made out of cast aluminum and includes a washable and reusable filter which is huge. The oversize filter flows so well, that you can easily hear the air passing through it when you rev the engine or accelerate. It has a very distinct and low sound and to our ears, it even made the exhaust sound deeper.
The air cleaner comes with all the necessary mounting hardware and instructions, so you shouldn’t have any issues installing it. We didn’t even have to fiddle around with the filter to get it seated correctly and symmetrically.
One interesting thing about this filter is that it removes the oil breather tubes that go across the throttle body. This is great for performance as nothing will be blocking the airflow, but it doesn’t really work with an oil catch can. If you are running a breather bypass, then you will be better off with a different air cleaner.
With that said, the K&N Street Metal RK-3956 provides outstanding air flow, deletes the oil breather tubes, and makes the intake sound mean. It’s for sure one of the best stage 1 cleaners for the Harley Davidson M8.
2. Arlen Ness 90° Monster Sucker
Quite an interesting name for an air filter, but it’s one of our personal favorites non the less. The Arlen Ness 90° Monster Sucker is a great choice for those who are looking for a bit more style on their motorcycle and like how cone-style air filters look.
The air cleaner extends to the front with a 90° pipe and the cone filter itself is huge. This air cleaner is definitely an eye-catcher and that’s one of the main reasons why we love it. The filter body has a glossy black finish and really makes the whole bike look sleek.
Now, since the cone filter is so huge, it has the biggest surface area of any air cleaner that we’ve seen. Not only does the cone filter suck air from the sides, but it also gets a huge amount of airflow through the top of the cone.
The 90° Monster Sucker air cleaner extends to the side quite a bit, but we did not have any trouble with the filter hitting our legs (6’2 tall). But then again, if you are over 6’5 tall, then your knees might reach the filter.
Lastly, the biggest drawback to this air cleaner is that it also deletes the oil breather tubes, so there is no way to use an oil catch can with the 90° Monster Sucker air cleaner without having to drill holes into it. But if you’re an experienced DIYer, then it can be done.
Here’s a great video by Rona’s Workshop detailing the whole process:
3. Vance & Hines Rogue VO2
If you’ve got a Vance & Hines 2-into-1 upswept exhaust on your Harley, then the Rogue VO2 is the perfect air cleaner to compliment that stunning exhaust. Better yet – the Rogue VO2 is cleverly designed to allow you to run a breather bypass mod or a catch can!
The Vance & Hines Rogue VO2 is a very stylish air cleaner with a black anodized backing plate, black filter element, and chrome cover Vance & Hines logo. It’s classy, elegant, and practical since you can wash it and reuse it.
While this air cleaner is not huge, like the other ones on our list, most of its surface area is filter material. This allows it to let in a surprisingly large amount of airflow into the Milwaukee 8 engine – definitely more than enough for a stage 1, 2, 3, or even 4 M8.
Now, we all love Vance & Hines for their prestige quality, and the Rogue VO2 definitely delivers with its clever oil breather tube design. Unlike most air cleaners, the Rogue VO2 leaves the breather bolts outside, which allows you to easily run a breather bypass or a catch can – both of which are extremely good mods for your engine. Just connect your bypass or catch can hoses, and you’re done.
All in all, the Vance & Hines Rogue VO2 is a great air cleaner for those who want the best of both worlds: style and functionality. The chrome cover screams prestige and the ability to do a breather bypass is a just cherry on top.
4. Happy-motor Turbine Filter
If you’re on a budget (like most people these days) yet still want an equally beautiful and free-flowing air cleaner for your Harley Davidson M8, we recommend the Happy-motor Turbine Filter.
This air filter is very inexpensive, yet very effective thanks to its turbine-style design, which is nearly identical to the Roland Sands Turbine Cleaner. The filter element makes up most of the air cleaner’s surface area, including the sides and even the front, thus you will have no problems getting airflow through even for a stage 4 Milwaukee 8.
It does come with a rain sock, which is a nice bonus, but the biggest drawback (at least to us) is that this air cleaner is not compatible with a catch can or a breather bypass. The breather tubes are hidden and internal, which makes it impossible to rout them to a catch can.
To sum up, it looks great, seems to be made well, and is also washable and reusable. At this price point, it’s hard to find a reason not to go with this Turbine Filter.
5. Clarion See-Through Air Cleaner
If you’re fascinated by the mechanical inner workings of your Milwaukee 8 and want to show it off to the world, then we’ve got just the air cleaner for you – the Clarion See-Through air cleaner by Happy-motor.
This beautiful and minimalistic air cleaner will let you see your bike’s throttle plate move and regulate air whenever you twist the throttle. It’s a great conversation starter and will definitely turn some heads.
The best part about this air cleaner is that it doesn’t have a center screw like some other cheap air cleaners have. This means that there is no chance that a metal screw will work itself loose over time and get sucked into the engine, potentially destroying the whole thing.
The Happy-motor Clarion See-Through Air Cleaner is a great way to show off the inner workings of your Milwaukee 8 engine and will definitely turn some heads. It’s also very well made and won’t break the bank. The only drawback is that it’s not compatible with a catch can or breather bypass, but if that’s not a problem for you, then you will definitely love this air cleaner.
How To Buy The Best Stage 1 Air Cleaner For HD M8
Now that we’ve gone over some of the best stage 1 air cleaners for Harley Davidson Milwaukee 8 engines, it’s time to talk about how to buy the best one for you.
There are a few things you need to keep in mind when shopping for an air cleaner and we will go over them now.
Avoid Small and Restrictive Air Cleaners
Obviously, the ideal air cleaner for a stage 1 M8 needs to be as free-flowing as possible, and that usually means bigger size.
The stock air cleaner on the Harley Davidson Milwaukee 8 has a tiny air intake hole, at least compared to most aftermarket performance air cleaners – mostly due to noise regulations and emissions.
When shopping for a new air cleaner for your Harley M8, keep an eye out for big air cleaners. The bigger the surface area of the filter element, the less obstruction to airflow.
Look for Washable and Reusable Air Cleaners
The second thing you want to look for in an air cleaner is that it’s washable and reusable. This will save you a lot of money in the long run as you won’t need to keep buying new air filters.
Choose The Style You Like The Most
The next thing you want to do is choose the style of air cleaner you like. This is completely a personal preference and will come down to what you think looks best on your bike.
Some air cleaners are more functional while others are more for show. It’s up to you to decide what you want.
With that said, make sure that you do not buy cheap air cleaners no matter how cool they look. Cheap filters wear out quickly from the vibrations, start letting dirty air through, fasteners loosen and sometimes even the whole filter falls apart while riding.
You definitely do not want your M8 to suck in broken parts of the air cleaner and destroy the engine.
Consider Breather Bypass Compatibility
Another thing you want to consider when buying an air cleaner is whether or not it’s compatible with a breather bypass.
A breather bypass is a great mod that will allow your engine to vent oil mist from the breathers into a catch can or the atmosphere. It will save your engine in the long run, as constantly burning oil and constantly causing carbon buildup on the piston won’t do any good to the Milwaukee 8.
If you want a breather bypass or a catch can on your Harley, then you need to make sure that the air cleaner of your choice does not cover the breather holes. The breather holes need to be unobstructed by the backplate and have enough room for the breather tubes.
Now, if you really like the air cleaner and it is not compatible with a breather bypass or a catch can, then you can drill holes into the filter, tap them, and run breather tubes from there. It’s not ideal, but it is definitely possible.
Consider a Rain Sock for Protection From Rain
If you live in an area where it rains a lot, then you might want to consider getting a rain sock for your air cleaner. A rain sock is a simple piece of mesh fabric that goes over the air filter and protects it from rain.
They are cheap, easy to use, and will stop your engine from stalling in heavy rain.
Final Thoughts
So, there you have it – the best stage 1 air cleaners for Harley Davidson M8 engines.
Keep in mind the things we talked about when choosing an air cleaner and you will definitely find the best one for you.
Thanks for reading and ride safe!
Jake is the site’s primary contributor.
Motorcycles and automotive repair have been a big part of his family for generations, therefore it’s only natural that he decided to become a heavy-duty diesel tech.
Outside of work, you’ll find Jake restoring and riding rare street bikes and ATVs.