6 models in this file
Arlen Ness Air Cleaners: Big Sucker vs Sidekick
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Arlen Ness is one of the best-known names in American V-twin customizing, and its air cleaners are among the most common first upgrades on Harley-style motorcycles. The Big Sucker line is the brand’s signature: a performance air filter kit built around a one-piece aluminum backing plate that routes crankcase breathers internally, so the bike looks clean and breathes more freely. Alongside it sit stylized options such as the Sidekick and the oval Stage 2 cleaners.
These six listings cover Big Sucker kits at Stage 1 and Stage 2, a replacement upgrade filter, a black oval Stage 2 cleaner and a titanium Sidekick. They differ in stage, finish and, importantly for buyers, how much detail each listing provides about fitment.
A quick word before the model rundown: most of these listings are thin. Only one, the 18-819 Stage II kit, lists fitment. For the rest, confirm with your bike’s year and model and the manufacturer’s application chart before ordering. We have kept to what each listing states and flagged the gaps.
The line-up at a glance
Arlen Ness Motorcycle Air Cleaners Compared
| Model | Type | Finish | Fitment in listing | Weight |
|---|---|---|---|---|
| Arlen Ness 18-500 Big Sucker Performance Kit | Big Sucker kit | Not listed | Not listed | Not listed |
| Arlen Ness 600-169 Oval Stage 2 | Oval air cleaner, Stage 2 | Black | Vehicle specific, not detailed | Not listed |
| Arlen Ness 81-312 Sidekick | Sidekick air cleaner | Titanium | Not listed | 4.45 pounds |
| Arlen Ness 18-306 Big Sucker Stage I | Big Sucker kit with cover | Smooth black | Vehicle specific, not detailed | Not listed |
| Arlen Ness 18-819 Big Sucker Stage II | Big Sucker kit with cover | Chrome | Twin Cam, Evo, Sportster (detailed) | 2 pounds |
| Arlen Ness 600-099 Big Sucker Upgrade Filter | Replacement filter | Not listed | Not listed | 1.3 pounds |
No. 1 of 6 · Arlen Ness
Arlen Ness 18-500 Big Sucker Performance Air Filter Kit for a Clean Breather Setup
9.4/10 Our score
Best for: Riders wanting the core Big Sucker design
Pros
- One-piece aluminum backing plate
- No banjo fittings or hoses
- Closed-loop breather routing
Cons
- Fitment not listed
- Cover style not described
The Arlen Ness 18-500 Big Sucker Performance Air Filter Kit is the base Big Sucker design. Its defining part is a one-piece aluminum backing plate that doubles as a carburetor support bracket. The listing says this eliminates the need for banjo fittings, hoses and filter breather passages, because the breathers exit at the mouth of the carburetor or throttle body, creating what Arlen Ness calls a virtually closed-loop system.
In plain terms, crankcase vapors are routed straight back into the intake instead of through external hoses, which tidies up the side of the engine and removes parts that can leak or come loose. The listing gives the shape as oval and round, but it does not name the stage, the cover style, the filter type or which motorcycles it fits. The specifications also list 109-0205 as a model number, which is confusing because another kit here uses that number as a cross-reference.
This kit suits riders who already know their application and want the core Big Sucker backing plate design. If you want a clearly documented fitment list and filter details before you buy, the 18-819 Stage II kit is the better-described option.
No. 2 of 6 · Arlen Ness
Black Oval Air Cleaner Stage 2 by Arlen Ness for a Dark Custom Look
8.0/10 Our score
Best for: Riders wanting a black oval Stage 2 look
Pros
- Stage 2 oval design
- Black finish
- Vehicle-specific fit
Cons
- Listing gives almost no details
- Fitment not listed
The Black Oval Air Cleaner Stage 2 by Arlen Ness, part 600-169, is an oval-shaped Stage 2 cleaner in black. The listing classifies it as a performance part with a vehicle-specific fit, but it does not say which vehicles, and it gives no details on filter media, breather design or what comes in the box.
Oval air cleaners are a popular styling choice because they follow the traditional shape of many stock covers while still opening up the intake. For touring riders, a black finish is also forgiving: road grime, bug splatter and water spots are less obvious than on chrome after a long highway day.
Choose this one if you want the Arlen Ness oval air cleaner shape in black and can confirm fitment with the seller or Arlen Ness first. For a fully documented Stage II option, look at the 18-819.
No. 3 of 6 · Arlen Ness
Arlen Ness Sidekick Titanium Air Cleaner for Side-Mount Style
9.8/10 Our score
Best for: Riders wanting a side-mounted titanium style
Pros
- Titanium finish
- Sidekick side-mount style
Cons
- Fitment not listed
- 45 lbs, heaviest listed
The Arlen Ness Sidekick Titanium Air Cleaner, part 81-312, is a Sidekick-style cleaner in a titanium finish. The listing gives a weight of 4.45 pounds and package dimensions of 8 x 8 x 6 inches. Beyond the name, part number and finish, it does not describe fitment, filter type or included hardware.
Side-mounted designs like the Sidekick push the filter out and away from the engine, which is a big part of their visual appeal. For touring riders, that raises two practical questions to check on your own bike: whether the filter will sit where your right leg rests on long rides, and how exposed it will be to rain and road spray. Open performance filters generally take in more water in heavy rain than a stock enclosed box, so riders who regularly tour in wet weather often carry a rain sock or cover.
The Arlen Ness Sidekick air cleaner suits riders who want a distinctive custom look and are willing to check leg clearance and fitment for their model. Riders focused on a low-profile, proven setup may prefer a round Big Sucker.
No. 4 of 6 · Arlen Ness
Arlen Ness 18-306 Big Sucker Stage I Kit with Smooth Black Cover
9.8/10 Our score
Best for: Stage 1 riders wanting a smooth black cover
Pros
- Includes cover
- Smooth black finish
- Round shape
Cons
- Fitment not listed
- Confusing cross-reference part number
The Arlen Ness 18-306 Big Sucker Stage I Air Filter Kit comes with a cover in a smooth black finish and a round shape. It is listed as a performance part with vehicle-specific fit, though the specific vehicles are not named. The OEM equivalent part number is given as 109-0205.
A Stage 1 kit is typically the entry step in an intake upgrade: it replaces the stock air cleaner with a freer-flowing filter while leaving most other parts alone. Many riders pair it with exhaust changes and a fuel map adjustment, since more air generally needs matching fuel. The listing itself does not describe tuning requirements, so check with your dealer or tuner for your model.
The Arlen Ness Big Sucker Stage 1 in smooth black suits riders who want a clean, understated look with the Big Sucker design. If you want a larger filter and a documented fitment list, step up to the 18-819 Stage II.
No. 5 of 6 · Arlen Ness
Arlen Ness 18-819 Chrome Big Sucker Stage II Kit for Twin Cam, Evo and Sportster
9.8/10 Our score
Best for: Twin Cam, Evo and Sportster owners
What the listing says
- Features a one-piece aluminum backing plate/carb support bracket with patented hidden Breather technology and radius air…
- Eliminates the need for banjo Fittings, Hoses and filter
- Breather passages exit at the mouth of the carburetor/throttle body, creating a virtually closed-loop system
- Kit Includes a 20% larger high-performance filter and Steel outer cover.
- Pre-oiled filters Available in two styles: standard or stainless-steel jacketed
- Fitment 99-17 Twin Cam Models (Except: 99-01 Fuel Injected FLT & FBW models), 99-01 Fuel Injected FLT…
Pros
- Detailed fitment list
- 20% larger filter
- Water-resistant washable synthetic filter
- Hidden breather, radius inlet
Cons
- Chrome needs regular polishing
- Excludes some 99-01 FLT models
The Arlen Ness 18-819 Chrome Big Sucker Stage II Air Filter Kit with Cover is the best-documented product in this lineup. It uses the one-piece aluminum backing plate and carb support bracket with patented hidden breather technology and a radius air inlet, and it eliminates banjo fittings, hoses and external filter breathers by routing breather passages to the mouth of the carburetor or throttle body.
The kit includes a 20% larger high-performance filter and a steel outer cover in chrome. Arlen Ness says its synthetic filters are water resistant, do not require oil, and are washable and reusable, which is a real advantage for touring riders who ride through rain. The listing also notes that pre-oiled filters are available in standard or stainless-steel jacketed styles. The kit weighs 2 pounds.
Fitment is listed as 1999-2017 Twin Cam models (except 1999-2001 fuel-injected FLT and fly-by-wire models), 1999-2001 fuel-injected FLT Twin Cam, 2008-2016 FLT Twin Cam fly-by-wire models, 2016-2017 Softail and FXDLS fly-by-wire, 1993-1999 carbureted Evo, and 1988-2018 XL Sportster models. The listing’s two statements about 1999-2001 fuel-injected FLT models seem to contradict each other, so check that one carefully if it applies to you. This is the Arlen Ness Big Sucker Stage 2 we would point most touring riders to.
No. 6 of 6 · Arlen Ness
Arlen Ness Big Sucker Upgrade Air Filter for Existing Kits
9.4/10 Our score
Best for: Existing Big Sucker owners upgrading filters
Pros
- Replacement upgrade filter
- 3 lbs
Cons
- Compatible kits not listed
- Filter only, no cover or plate
The Arlen Ness Big Sucker Upgrade Air Filter, part 600-099, is a replacement filter element rather than a complete kit. The listing gives a weight of 1.3 pounds and no other details: it does not say which Big Sucker kits it fits, what media it uses, or whether it needs oiling.
It suits riders who already run a Big Sucker and want a fresh or upgraded filter. Match the part number against your existing kit before ordering. Keeping an intake filter clean matters on any engine; the same principle applies whether it is a motorcycle or the small engine air filter on your mower.
Before you choose
How to Choose the Right Arlen Ness Air Cleaner
Fitment first. Only the 18-819 lists specific model years. For every other product here, confirm your year, model and whether you have a carburetor, fuel injection or fly-by-wire throttle before buying.
Stage 1 or Stage 2. Stage 1 kits like the 18-306 are the simpler, entry-level upgrade. Stage II kits like the 18-819 add a larger filter and more airflow. More airflow usually works best with matching exhaust and fuel tuning, so plan the whole setup, not just the air cleaner.
Rain exposure and filter type. Touring riders spend hours in changing weather. The 18-819 listing says its synthetic filters are water resistant, washable and need no oil, which suits wet climates. Other listings do not specify their filter media. Open side-mount designs can be more exposed to spray.
Leg clearance and style. Round Big Sucker covers are relatively compact. The Sidekick and oval styles are more visual statements; test-fit or check photos of your model to make sure your right leg sits comfortably on long highway days.
Finish and upkeep. Black finishes hide road grime, while chrome and titanium look best when kept clean. Washing the bike regularly with a mild all-purpose exterior cleaner diluted properly, and rinsing well, keeps covers looking sharp.
Questions people ask
FAQ
What is an Arlen Ness Big Sucker?
It is Arlen Ness’s performance air filter kit, built on a one-piece aluminum backing plate that routes crankcase breathers internally to the carburetor or throttle body, eliminating external banjo fittings and hoses.
What is the difference between Big Sucker Stage 1 and Stage 2?
Stage 1 is the entry-level kit. The Stage II 18-819 adds a 20% larger high-performance filter. Check your tuning needs with either.
Which Harley models does the Arlen Ness 18-819 fit?
The listing names 1999-2017 Twin Cam models with exceptions, 2008-2016 FLT fly-by-wire, 2016-2017 Softail and FXDLS fly-by-wire, 1993-1999 carbureted Evo and 1988-2018 Sportster models.
Do Arlen Ness filters need oil?
The 18-819 listing says its synthetic filters do not require oil and are washable and reusable, and that pre-oiled versions are also available. Other listings do not specify.
Is the Arlen Ness 600-099 a complete kit?
No. It is listed as a Big Sucker upgrade air filter only, with no cover or backing plate.
Are Arlen Ness air cleaners good in the rain?
Arlen Ness describes its synthetic filters as water resistant. Any open performance filter is more exposed than a stock box, so touring riders in wet regions often carry a rain cover.
Prices, specifications and the feature lines above are read from the product listing and can change without notice. Scores are out of 10, based on listed specifications and buyer feedback; nothing on this page is written from handling the product.
