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TTR 125 Jet Kit Installation Instructions

Important: All appropriate safety equipment and gear must be used during the installation of this or any other ProCycle product including any time you work on a vehicle. ProCycle accepts no responsibility for injuries or damage incurred during the installation of any products.

Be safe – no smoking or open flame. Don’t get gasoline on your skin. Wear eye protection. Use ventilation to avoid buildup of explosive fumes.

Parts Supplied

  • 17.5 & 20 pilot jets
  • 110 & 112.5 main jets


We highly recommend having a service manual on hand for carburetor removal and installation details.

  1. Drain the fuel from carburetor and remove the carburetor from the bike.
  2. Replace the jets with the ones that match the configuration of your motorcycle.

    ConfigurationPilot jetMain jet
    Stock exhaust17.5110
    Aftermarket exhaust17.5110
    Aftermarket air filter and exhaust17.5112.5


Evaluate all adjustments only with the motor fully warmed up (after at least 5-10 miles of spirited riding).

Idle fuel mixture:

Turn the idle mixture screw inwards (clockwise) until the idle speed starts to drop or become slightly rough. Screw the mixture screw out (counter-clockwise) until the idle just smooths out.

Pilot Jet:

Should you desire a richer low end, use the 20 pilot jet.

Main jet:

To test the main jet selections run the bike at wide open throttle in 4th gear on a level road. When the bike is pulling cleanly at a good high RPM & wide-open throttle slowly back off on the throttle to about 7/8 throttle. If the bike picks up speed or power as you slightly back off the throttle then you are running too lean on the main jet. If the bike only slows down slightly then your main jet selection is close. If it is too rich the exhaust note may sound flat as the motor revs out. If it is significantly too rich it may misfire as the revs climb.


The 2nd groove is a good starting point and will work well for most bikes. To go one step richer at midrange throttle, move the clip down to the 3rd groove. Conversely to set it one step leaner move the clip up to the 1st groove. Always count grooves from the top down.

The needle clip should be set on the highest groove (leanest setting) that still provides smooth steady speed engine operation and good throttle response.