If you are running a 38 pilot and looking for something leaner - then you are "pulling over" ... You shouldn't have your idle screw turned all the way in - if you do - then fuel is provided via needle versus pilot at low rpms... This is typically the case if you are running a 38 pilot and looking for a leaner pilot. What drives one in this direction is a bad needle along with bad idle screw setting... (as a start).
Start with getting a good needle - cut slide to #8 from #7 helps. Make sure you reset idle and air mixture screws when you switch over to the better needle - I would start with 42-45 pilot and 178 main - this may be different depending on fuel in your country... Aim for 2 to 2.5 turns out on air screw, and back out the idle screw (espcially if it is cranked all the way in to the point of being coil bound by the spring)- this will give you more fuel/air on bottom from pilot circuit in carb. This circuits in the carb need to be "better separated" - and this helps in this regard.
As was previously noted - the needle jet, the orifice that the needle slides into, becomes oval in shape with hours on the bike - it is not replaceable. Ron and RB-Designs was fixing these when he did his "carb mod" - which really addresses the pilot circuit sensitivity (or lack thereof) in the pwk38...
jeff
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