Jetting



3 replies to this topic
  • ENGMEDIC19

Posted March 25, 2002 - 03:45 PM

#1

when you change the main jet, do you have to adjust the pilot air screw as well? If you do which way do I turn it when you install a smaller main? Im going from a 170 back to a 165. The pilot screw is at about 2 1/2 turns out. The bike is surging and poping on exceleration. Thanks for any help.

  • Taffy

Posted March 25, 2002 - 10:33 PM

#2

get rid of that needle.

get an EMN or EMM in the meantime drop the needle once and if it goes well try it again = twice.

if you do drop the MJ check it with a proper run on the road. it will only have changed 3/4 speed plus.

so MJ
needle once
needle twice?

leave the pilot setting. you need a needle.

Taffy

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  • Mark_Cantrell

Posted March 26, 2002 - 03:57 AM

#3

Listen to Taffy, we all do. The stock screw recessed underneath the engine side of the carb is a fuel screw, in lean, out rich. It works in the same throttle position ranges as the pilot jet. If the screw is in too far (less than 3/4 turn out?) get a smaller pilot and if too far out (greater than 2 turns?) get a larger pilot jet.

There is a Sudco aftermarket pilot air screw that replaces the pilot air jet. I can't figure out if it (pilot air screw or pilot air jet) supplies air to the emulsion nozzle of the pilot jet and more air is richer or more air is leaner.

Anyway, if your question was "If I change the main jet, do I have to change the pilot screw or jet?", the answer is there is no direct reason. The two are independent affecting different throttle positions. If you are going from riding at 40 degrees to riding at 90 degrees and change the main jet for that reason (or altitude), yes, change the main jet for 1/2 to full throttle, the needle or needle position for 1/4 to 1/2 throttle, and the pilot jet or screw for low throttle positions.

mwc

  • ENGMEDIC19

Posted March 26, 2002 - 06:28 PM

#4

THANK YOU. I WILL LOOK FOR THE SCREW AT SUDCO.




 
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