Air Jet



2 replies to this topic
  • James_in_New_Mexico

Posted March 20, 2001 - 05:08 AM

#1

Need to know if I need to change air jet and where to get it? And, is it the one next in the carb by the main and the pilot? If so, my yamaha dealer says he can only order up to #70 because that is what is on the fische.

5000 ft
YZ timed
air box lid removed
stock pipe w/core removed
not sure off the top of my head about the jets:
Main = 168
pilot = 48

Thanks for any help you can give.

James

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  • James_Dean

Posted March 20, 2001 - 12:48 PM

#2

James in NM,

There are 2 air jets on the intake side of the carb, not in the float bowl. The jet you were looking at was probably for the choke circuit.

The main air jet (#200) is for high throttle tuning along with the main (fuel) jet. #200 is the maximum size available. We have been discussing going beyond this in the FCR tuning thread but this is looking for max power beyond the needs of most. This is an ongoing search.


The pilot air jet (~#75-WR, #100-YZ) is for low throttle tuning and will apply to most riders. You don't need to replace it unless you are looking for better response just off idle. By going to a bigger pilot jet such as #45 or #48, the pilot air jet can be increased to a #100 or #125 to get better torque from idle. This helps keep the pilot screw (for fuel) in the range of 1-2 turns. The 3 components work together- pilot jet, pilot air jet, pilot screw.

If you want a #100 pilot air jet it is Yamaha P/N 7A9-14943-27 (please check that first in the YZ fische).

There have also been discussions on replacing the pilot air jet with a pilot air screw. It is surprising that Keihin machined a recess behind the pilot air jet for this feature in the carb and Yamaha did not use it. The pilot air screw allows a wide range of adjustments instead of buying assorted jets.

The pilot air screw with spring and a large assortment of jets are available from Sudco.

James Dean

  • James_in_New_Mexico

Posted March 20, 2001 - 01:32 PM

#3

Thanks JD, you and the rest of the members of this sight have helped me quite a bit and the need to post questions are far and few between because they are usually asked and answered before I need to post!!!!

James




 
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