Personally i would buy the KLX needle kit from Eagle Mike and use the correct jet for your area and if asked he will suggest which to use.....I'm roughly at sea level and used the 145 main and the clip in the centre or third slot with a 20 thou shim under it which is half a notch jump. BUT, I do have a none stock engine but am running the LEXX so imho you should use roughly the same jet and position, but it's a complete kit and the needle is completely adjustable. The 22 cent mod is a silly minute adjustment that we all did when we were noobs, and ok it did make a small small difference but for the cost of the KLX kit....simply put go for it!, That and a UNI filter and 4 one inch holes in the top of your airbox.
For just the Lexx you probably could get away with the stock jetting, but I agree with the others; the KLX kit is the way to go. Go ahead and drill the airbox lid or do the L-mod (it does help flow with no real downside) but at the very least pull that snorkle!
Follow the instructions from EM on the jetting. My bikes both have the 4 - 1" holes, snorkle-ectomy, Uni/TwinAir, FMFQ4/LeoVince X3 and both run a 142 main, second position , no washer under and 2 turns on the fuel screw. Jetting is spot on at those settings; I live at 1200 ft above sea level and regularly ride to 5000 ft.
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