DOMA Expansion Chamber for YAMAHA DT 125 1993-2003

The DOMA 100100 expansion chamber is designed for YAMAHA DT 125 from 1993 to 2003. 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: 100100
• 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 · CENTAURO
• Spark plug : NGK 3981 · NGK 2411

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:
YAMAHA DT 125 2003
YAMAHA DT 125 2002
YAMAHA DT 125 2001
YAMAHA DT 125 2000
YAMAHA DT 125 1999
YAMAHA DT 125 1998
YAMAHA DT 125 1997
YAMAHA DT 125 1996
YAMAHA DT 125 1995
YAMAHA DT 125 1994
YAMAHA DT 125 1993