Carb Tuning

The carburettor on the XR125L is a simple one. There is no automatic choke or temperature sensitive tuning. For smooth operation and good running it needs to be kept clean, and tuned.

Tools Required

• Gunson Colortune kit (12 mm)*

• Flat head screwdriver

• 90 degree screwdriver (or asbestos fingers)

• A digital tachometer

*I have no affiliation with Gunson, I just find tuning a carb so much quicker using a colortune.

How to Tune a Carburettor

• Ride the bike for 20 minutes or more until it is fully up to temperature

• Remove the spark plug - caution it will be hot

• Install the colortune spark plug

• Wrap the digital tachometer's sensor wire around the HT lead

• Start the engine

• Adjust the idle speed so it is below 1,800 RPM (this is to make sure the engine is running on the idle jet, not the main jet), but where the engine will still run with the choke off

• Adjust the idle mixture screw (be cautious of the exhaust, this is where the 90 degree screwdriver helps) until the colour of the flame is white (if it's blue it's running lean so back out the idle screw, if it's yellow it's running too rich so screw in the mixture screw)

• Adjust the idle speed back down to 1,400 RPM

• Done!