What is often missed when switching needles is to reset the idle screw.
also, you might end up at up to 2.5 turns out on the airscrew and everything will be fine...
The idle screw needs to be backed out to bring the slide and needle down to better separate the idle and mid circuits in the carb.
One way you can tell if your jetting is still "non-optimal" is if your air screw (idle mixture screwi) still has little effect.
In my opinion, if have a "good needle" and you are down to a 38 pilot and looking for something leaner - then your idle might still be cranked up too far.
My experience is that - set up properly - with better needle installed, jets & idle and air screw settings good - it will start easily and idle too... (BTW - a yamaha yz kickstarter helps too).
jeff
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