What Do Pre-Filter Plugs Do on the KTM 790/890 Adventure?
Short answer: pre-filter plugs are oiled foam elements that fit the intake openings of the KTM 790 Adventure, 890 Adventure, and Husqvarna Norden 901. They stop heavy dust at the front door, before it ever reaches the airbox and the main filter. The FunnelWeb Pre-Filter Plugs (7337, $59.95) come as a set of two and are included in the Full Kit (7336).
Filtration works best in stages
Every gram of dust the engine does not eat was stopped somewhere along the intake path, and the earliest stage is the cheapest place to win. Coarse, heavy dust (roost from the rider ahead, sand kicked up in a wash) is easy to catch at the intake opening while it is still moving slowly. Stop it there and the main filter spends its capacity only on fine dust, which is the part that actually threatens the engine.
What changes when you fit them
- The main filter stays cleaner, much longer. On dusty group rides the plugs take the visible beating.
- Mid-trip service gets trivial. The plugs are the most accessible filtration on the bike. Refresh them at camp in minutes and leave the airbox sealed until home.
- Fewer airbox openings. Every time the airbox opens in dusty country there is a chance for dirt to fall somewhere it should not. Fewer openings is itself protection.
Do they restrict airflow?
Clean, oiled foam flows freely. The airflow worry that matters is a loaded main filter deep into a dusty day, and the plugs exist to prevent exactly that. Riders chasing every last horsepower on pavement can remove them for street stints in minutes; riders in dust should leave them in.
Frequently asked questions
Do the plugs replace the main filter?
No. They are stage one of a layered system. The main filter on the FWF frame (7339) remains the final guard. Run both; that is the design.
How do I service them?
Same as any FunnelWeb element: wash, dry, re-oil, reinstall. Never use No-Toil brand oil or cleaner; it attacks the foam adhesive. Guide: cleaning and re-oiling foam filters.
Do they fit the Norden 901 and the 790?
Yes. The 790 Adventure, 890 Adventure, and Norden 901 share the intake design.
Related: the complete KTM 790 & 890 Adventure air filter guide and why the stock filter lets dust through.