KTM · PowerParts · Exhaust systems
The KTM FMF Fatty Expansion Chamber is a KTM PowerParts exhaust component built for 2-stroke offroad performance, delivering a full sound and improved power delivery. Designed as a durable upgrade, it suits riders looking for a stronger expansion chamber construction paired with recognizable FMF Fatty character.
This version carries part number A40505907000 and features a Nickelplated surface. It is made from extra strong sheet steel for added robustness in demanding riding conditions. For a matched setup, combination with an FMF silencer is recommended.
Performance
Built to help sharpen how the engine delivers power, the FMF Fatty Expansion Chamber focuses on better power delivery for 2-stroke offroad riding. It is intended for riders who want a performance-minded exhaust change that supports strong, responsive output.
Construction
Constructed from extra strong sheet steel, this expansion chamber emphasizes durability for offroad use. The robust material choice is aimed at standing up to real riding conditions while maintaining the intended FMF Fatty expansion chamber performance.
Design
A Nickelplated finish is specified for the surface, giving the chamber a distinct plated exterior. This surface specification is part of the overall build of the KTM FMF Fatty Expansion Chamber and complements its heavy-duty steel construction.
Performance
This KTM PowerParts FMF Fatty Expansion Chamber is designed to deliver a full sound along with better power delivery in a 2-stroke offroad exhaust system. It is positioned as a functional upgrade for riders focused on performance and feel, while keeping the recognizable FMF Fatty expansion chamber design at the core of the setup.
Durability
Durability is supported through extra strong sheet steel construction combined with a Nickelplated surface. Together, these specifications define a chamber built to handle offroad use while maintaining its intended performance. For riders planning a coordinated exhaust package, combination with an FMF silencer is recommended.
Installation
This expansion chamber is listed as compatible with the models shown in the vehicle compatibility table on the page. Confirming the exact application details there helps ensure the correct match to the motorcycle before installation.
| Part Number | A40505907000 |
|---|---|
| Product Line | KTM PowerParts |
| Category | Exhaust systems > 2-stroke Offroad |
| Surface | Nickelplated |
| Approvals | CCCUO |
| Model — Model Years |
|---|
| 65 SX — 2024–2027 |
Vehicle compatibility as captured from KTM for article number A40505907000.
KTM approval notice: Closed Course Competition Use Only.
