KTM · PowerParts · Exhaust systems
The KTM FMF Factory Fatty Expansion Chamber is a KTM PowerParts exhaust component designed for 2-stroke offroad machines. Built from extra strong sheet steel with a natural/untreated surface, it’s aimed at riders who want a more responsive feel and improved overall drive from the engine while keeping a full, pronounced sound character.
This expansion chamber is offered as part number A44005907001. It is listed for the KTM models shown in the vehicle compatibility table below.
Construction
Made from extra strong sheet steel, this expansion chamber is built to handle the demands of offroad riding. The robust material choice supports long-term use in harsh conditions while maintaining the intended shape and performance characteristics of the pipe.
Design
The pipe features a natural/untreated surface. This finish keeps the expansion chamber true to its raw, race-focused look and aligns with the product’s straightforward construction approach as described in the specifications.
Performance
Designed to provide better power delivery, the FMF Factory Fatty Expansion Chamber helps deliver a stronger, more effective response across the riding range. It’s also described as producing a full sound, emphasizing the classic 2-stroke exhaust character.
As an expansion chamber in the Exhaust systems > 2-stroke Offroad category, this component is focused on performance characteristics specific to 2-stroke engines. The design is intended to improve how power is delivered, helping the engine feel more effective under load while preserving the full sound noted in the product details.
For riders planning a complete exhaust setup, the product data recommends combining this expansion chamber with an FMF silencer. Matching components can help align the overall system with the pipe’s intended behavior and sound profile, making it easier to build a cohesive exhaust configuration for the compatible models listed.
This KTM PowerParts expansion chamber is identified as used by factory racing. That association highlights its performance intent and positions it as a competition-oriented option within KTM’s accessory line, reflecting the same type of component selection seen in high-level race environments.
| Part Number | A44005907001 |
|---|---|
| Product Line | KTM PowerParts |
| Category | Exhaust systems > 2-stroke Offroad |
| Surface | Natural/untreated |
| Approvals | CCCUO |
| Factory Racing | USED BY FACTORY RACING |
| Factory Racing | Used by factory racing |
| Model — Model Years |
|---|
| 250 EXC — 2024–2025 |
| 250 EXC Champion Edition — 2025 |
| 250 EXC Six Days — 2024–2025 |
| 250 SX — 2024–2027 |
| 250 XC — 2023–2027 |
| 250 XC-W — 2024–2027 |
| 300 EXC — 2024–2027 |
| 300 EXC 6Days — 2026 |
| 300 EXC 6DAYS — 2027 |
| 300 EXC Champion Edition — 2025–2026 |
| 300 EXC Hardenduro — 2024–2027 |
| 300 EXC Six Days — 2024–2025 |
| 300 SX — 2023–2027 |
| 300 XC — 2023–2027 |
| 300 XC-W — 2024–2027 |
| 300 XC-W Champion Edition — 2025 |
| 300 XC-W Hardenduro — 2024–2027 |
Vehicle compatibility as captured from KTM for article number A44005907001.
KTM approval notice: Closed Course Competition Use Only.
