Needle Clip Position

 Needle clip position is a small but important tuning part for our two stroke racing engines.  Many times our track side support technicians just throw out the term P2, P3.5, or Position 2.  Many times we make the assumpition that everyone knows what we are talking about, but sometimes this is not the case.  

To start, the needle clip is the small "e" style clip that snaps into the grooves on a supplied needle.  Referencing the Keihin needle, it will have 5 grooves.  SwedeTech support techs always refer to the top groove as P1, or Position 1.  On a Keihin needle, we count down from the top, P1, P2, P3, and so on.

If we say go 1 down, you will lower the clip down 1 groove.  Some applications such as the Dell'Orto VHSH 30mm carb and the SwedeTech Floating Needle holder have a clip and a clip washer.  You can use the washer for half steps.  

If the washer is on top of the needle clip, then the clip position is where the clip is located.  If the washer is under the needle clip, then the clip position is clip position plus half step.  

Needle clip in P2, washer on top of clip - Position P2

Needle clip in P2, washer on bottom of clip - Position P2 and a half

The top needle clip position is the leanest position available.  This is because the needle is sitting farther down the inside of the atomizer or emulsion tube, restricting the fuel flow for a longer period of throttle slide travel. 

The bottom needle clip position is the richest position available.  This is because the needle is sitting higher in the atomizer or emulstion tube, allow fuel to flow from the tube to the venturi at a shorter period of throttle slide travel.

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