i bought a piliot jet for my PD keihn carb thinking it was the neeedle jet. what does the pilot jet do anyways? does it have to do with 1/4 throttle to 3/4?

 

Its more for the 0-1/4 throttle range.The main jet is the one for1/4 to wide open

 

this is the full function of air and fuel.

Closed to 1/8 throttle—air screw and pilot/slow jet

1/8 to 1/4 throttle—air-screw, pilot/slow jet, and throttle slide

1/4 to 1/2 throttle—throttle slide and jet needle

1/2 to full open—jet needle, spray-bar/needle jet, main jet, and air jet

(Note: On many modern carbs the spray-bar/needle jet and air jets are fixed-diameter passages in the carburetor body and cannot be altered.)

got it from here

 

go to duncan racings web site (duncanracing.com) i believe they have an awsome page on carbs and jetting