FMF Fatty Expansion Chamber Pipe — KTM Husqvarna GASGAS 250 300 2-Stroke (55505907000)
FMF
SKU: 55505907000

FMF Fatty Expansion Chamber Pipe — KTM Husqvarna GASGAS 250 300 2-Stroke (55505907000)

Sale price$99.99 Regular price$299.99
Save $200.00

FMF Racing · Two-Stroke Off-Road

FMF Fatty Expansion Chamber

The pipe that built FMF's reputation in the dirt — tuned to fatten up the bottom-to-mid powerband on your 250/300 two-stroke for traction you can actually use.

SKU 55505907000

The Fatty isn't about chasing peak horsepower on a dyno sheet — it's about the part of the powerband you live in on a trail. FMF engineers the chamber volume and taper to broaden low-to-mid output, smoothing out the abrupt hit of a big-bore two-stroke into linear, hook-up power. The result is a bike that lugs through technical sections without fouling, drives off the bottom out of corners, and stays composed when the terrain gets nasty.

Every Fatty is CAD-designed and hand-welded in the USA from heavy-gauge nickel-plated steel, then built to bolt straight on using your bike's OEM mounting points. It's the off-road standard for a reason: proven power, proven durability, and a fit that doesn't fight you in the garage.

Why riders run it

  • Broader low-to-mid powerSmoother, more tractable delivery dialed for trail, enduro, and woods riding.
  • Sharper throttle responseMore torque off the bottom and cleaner roll-on when you need drive.
  • Built in the USACAD-engineered and hand-welded for consistent, repeatable performance.
  • Heavy-gauge steelNickel-plated construction made to survive roost, rocks, and tip-overs.
  • True bolt-on fitMounts to OEM hangers and points — no fab, no fuss.
  • System-readyEngineered to pair with FMF silencers (Turbinecore 2 / Q-Stealth) for a complete setup.

Specs

Component Expansion chamber (pipe only)
Material Heavy-gauge nickel-plated steel
Engine 250 / 300 two-stroke
Power character Broad low-to-mid, off-road tuned
Fitment KTM, Husqvarna & GASGAS · model years 2019–2023 (see chart)
Installation Direct bolt-on, OEM mounting points
Made in USA
SKU 55505907000
Heads up: This listing is for the expansion chamber (pipe) only. Confirm your exact model, year, and market in the fitment chart below before ordering.

Fitment Chart

KTM

2023
250 EXC EU
250 EXC Six Days EU
250 XC-W US
300 EXC BR · EU
300 EXC Erzbergrodeo EU
300 EXC Six Days CN · EU
300 XC-W US
300 XC-W Erzbergrodeo US
2022
250 EXC TPI EU
250 EXC Six Days TPI EU
250 SX EU
250 XC TPI US
250 XC-W TPI US
300 EXC BR
300 EXC TPI EU
300 EXC TPI Erzbergrodeo EU
300 EXC Six Days TPI ASEAN · CN · EU · PH
300 XC TPI US
300 XC-W TPI US
300 XC-W TPI Erzbergrodeo US
2021
250 EXC TPI EU
250 EXC TPI Six Days EU
250 SX EU
250 XC TPI US
250 XC-W TPI US
300 EXC BR
300 EXC TPI EU
300 EXC TPI Erzbergrodeo EU
300 EXC TPI Six Days CN · EU
300 XC TPI US
300 XC-W TPI US
2020
250 EXC TPI EU
250 EXC Six Days TPI EU
250 SX EU · US
250 XC TPI US
250 XC-W TPI US
300 EXC BR
300 EXC TPI EU
300 EXC Six Days TPI EU
300 EXC TPI Erzberg Edition EU
300 XC TPI US
300 XC-W TPI US
300 XC-W Six Days TPI US
2019
250 SX EU · US
250 XC US
300 XC US

Husqvarna

2023
TE 250 EU · US
TE 250 Heritage EU
TE 300 AR · EU · US
TE 300 Heritage EU · US
2022
TC 250 EU
TE 250i EU · US
TE 300i AR · EU · US
TE 300i Rockstar Edition EU · US
TX 300i US
2021
TC 250 EU
TE 250i EU · US
TE 300i EU · US
TE 300i Rockstar Edition EU · US
TX 300i US
2020
TC 250 EU
TE 250i EU · US
TE 300i EU · US
TE 300i Jarvis Edition EU · US
TX 300i US
2019
TC 250 EU
TX 300 —

GASGAS

2023
EC 250 EU · US
EC 300 EU · US
EX 250 US
EX 300 US
MC 250 EU
2022
EC 250 EU · US
EC 300 EU · US
EX 250 US
EX 300 US
MC 250 EU
2021
EC 250 EU
EC 300 EU · US
EX 300 US

 

KTM Fitment:

2023

  • 250 EXC (EU)
  • 250 EXC Six Days (EU)
  • 250 XC-W (US)
  • 300 EXC (BR)
  • 300 EXC (EU)
  • 300 EXC Erzbergrodeo (EU)
  • 300 EXC Six Days (CN)
  • 300 EXC Six Days (EU)
  • 300 XC-W (US)
  • 300 XC-W Erzbergrodeo (US)

2022

  • 250 EXC Six Days TPI (EU)
  • 250 EXC TPI (EU)
  • 250 SX (EU)
  • 250 XC TPI (US)
  • 250 XC-W TPI (US)
  • 300 EXC (BR)
  • 300 EXC Six Days TPI (ASEAN / CN / EU / PH)
  • 300 EXC TPI (EU)
  • 300 EXC TPI ERZBERGRODEO (EU)
  • 300 XC TPI (US)
  • 300 XC-W TPI (US)

  • 300 XC-W TPI Erzbergrodeo (US)

2021

  • 250 EXC TPI (EU)
  • 250 EXC TPI Six Days (EU)
  • 250 SX (EU)
  • 250 XC TPI (US)
  • 250 XC-W TPI (US)
  • 300 EXC (BR)
  • 300 EXC TPI (EU)
  • 300 EXC TPI Erzbergrodeo (EU)
  • 300 EXC TPI Six Days (CN / EU)
  • 300 XC TPI (US)
  • 300 XC-W TPI (US)

2020

  • 250 EXC Six Days TPI (EU)
  • 250 EXC TPI (EU)
  • 250 SX (EU / US)
  • 250 XC TPI (US)
  • 250 XC-W TPI (US)
  • 300 EXC (BR)
  • 300 EXC Six Days TPI (EU)
  • 300 EXC TPI (EU)
  • 300 EXC TPI Erzberg Edition (EU)
  • 300 XC TPI (US)
  • 300 XC-W Six Days TPI (US)
  • 300 XC-W TPI (US)

2019

  • 250 SX (EU / US)
  • 250 XC (US)
  • 300 XC (US)

Husqvarna Fitment:

2023

  • TE 250 (EU / US)
  • TE 250 Heritage (EU)
  • TE 300 (AR / EU / US)
  • TE 300 Heritage (EU / US)

2022

  • TC 250 (EU)
  • TE 250i (EU / US)
  • TE 300i (AR / EU / US)
  • TE 300i Rockstar Edition (EU / US)
  • TX 300i (US)

2021

  • TC 250 (EU)
  • TE 250i (EU / US)
  • TE 300i (EU / US)
  • TE 300i Rockstar Edition (EU / US)
  • TX 300i (US)

2020

  • TC 250 (EU)
  • TE 250i (EU / US)
  • TE 300i (EU / US)
  • TE 300i Jarvis Edition (EU / US)
  • TX 300i (US)

2019

  • TC 250 (EU)
  • TX 300

GASGAS Fitment: 

2023

  • EC 250 (EU)
  • EC 250 (US)
  • EC 300 (EU)
  • EC 300 (US)
  • EX 250 (US)
  • EX 250 (US)
  • EX 300 (US)
  • EX 300 (US)
  • MC 250 (EU)
  • MC 250 (EU)

2022

  • EC 250 (EU)
  • EC 250 (US)
  • EC 300 (EU)
  • EC 300 (US)
  • EX 250 (US)
  • EX 300 (US)

  • MC 250 (EU)

2021

  • EC 250 (EU)
  • EC 300 (EU)
  • EC 300 (US)
  • EX 300 (US)

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