Skip to main content

Optimal Carburetor Running Conditions

Jetting Technique:​

The 20mm ShengWay carburetor is notably straightforward to calibrate directly from the package. It is equipped with a #89 main jet and a #35 pilot jet.

Baseline Configuration:​

  • Utilize a #90 or #92 main jet.
  • Employ a #38 or #40 pilot jet.
  • Position the jet needle e-clip in the 3rd or 4th notch from the top.
  • Adjust the air screw to 1-1/2 to 1-3/4 turns out from seated.

Make incremental air screw adjustments inward to enrich the mixture by 1/4-turn at a time and observe the motorcycle's response. In certain carburetors, it may be necessary to adjust to within a 1/2-turn of fully seated to eliminate 98% of the off-idle hesitation. Depending on your altitude, you may need to adjust the clip on the needle up or down. My settings are based on sea level conditions.

Please note that the aforementioned settings are intended for use with an aftermarket or larger valved head, rather than the stock head. It may be prudent to experiment with the stock carburetor jetting initially, due to the smaller intake port of the stock head.