DOMA Expansion Chamber for HUSQVARNA TC 125, KTM SX 125 and GAS GAS MC 125 2019-2023

The DOMA 100404 expansion chamber is designed for KTM SX 125, HUSQVARNA TC 125 and GAS GAS MC 125 from 2019 to 2023. On a two-stroke, the expansion chamber isn't just a pipe: its cones send back a pressure wave that fills the cylinder better at the right rpm. Its shape gives the engine its character, and a dented pipe costs power.

Key features

• Handmade in Calais, France.
• 1 mm raw steel, laser-cut parts, pressed and then welded on a jig.
• Developed on the dyno and on the track.
• Works with the stock silencer or a Doma silencer.

Specifications

• Brand: DOMA
• Manufacturer part number: 100404
• Engine: 2-stroke

Who is it for?

• Stock pipe dented or cracked after a crash.
• Looking for more response and more power.

Good to know

Competition use only: this pipe is not road-legal.

Fitting tips

1. Reuse the stock connecting O-rings if they're in good condition (not included), or fit a new exhaust gasket.
2. Offer up the pipe without forcing it, fit all the mounts, then tighten.
3. Warm up the engine and check for leaks at the joints.
4. Check the colour of the spark plug after the first few rides.

Why DOMA?

A French workshop based in Calais since 1992, Doma Racing designs and handbuilds two-stroke expansion chambers and silencers. A 125 world title in 2000 with Grant Langston and original equipment at KTM: a brand run by two-stroke enthusiasts.

Spare parts and items to plan

• Exhaust gasket : ATHENA S410270012020 · ATHENA M753004300094
• Spark plug : NGK 2707 · NGK 3230

Frequently asked questions

Do I need to change the silencer?
No: the pipe works with the stock silencer or a Doma silencer.

Is it road-legal?
No: for competition use on closed circuits only.

Compatibility

Check the exact model and year of your bike in the list below before ordering.

Fits:
GAS GAS MC 125 2023
GAS GAS MC 125 2022
GAS GAS MC 125 2021
HUSQVARNA TC 125 2022
HUSQVARNA TC 125 2021
HUSQVARNA TC 125 2020
HUSQVARNA TC 125 2019
KTM SX 125 2022
KTM SX 125 2021
KTM SX 125 2020
KTM SX 125 2019