Kx100 too lean

I have a stock 2016 kx100. It’s getting too much air from somewhere. The farther I turn the air screw in the better it revs off idle. Went up , way up , on the pilot jet with the same results. Rebuilt the motor, new crank seals , bearings, cylinder and piston (stock size) checked ring end gap motor ran decent for break in for an hour or so then lost compression. Looks like a lean seize. Lots of damage to the cylinder and piston/ ring on the exhaust side. Turns out the carb air screw was turned all the way in so it still got air from somewhere. Replaced cylinder and piston. Did a leak down test and it’s losing a very minimal amount , well less than 1 psi per minute. Again , carb is oem spec for jets, slide , needle size etc. Any thoughts on where this air may be coming from ?