KLX 140 Carb adjusting

My daughter has a 2016 KLX 140L that has been really tough to get started since I bought it a few months ago. The bike has less than 10 hours on it now.

I'm no carb guru so I bought a jet kit online and removed the snorkel/drilled a few holes in the air box and it will start up easily without using the choke now. The jet kit had a 105 main jet and 40 slow jet. The idle was pretty low so I turned up the idle screw a little and it will idle properly for 10 seconds or so then the idle will increase for a little bit then drop back down.

I think I may need to adjust the air mixture screw but not sure how to go about it. Is there a procedure of adjusting the air mixture screw and idle screw to get it to idle properly? Thanks.

If it starts easily without the choke, it's probably running a little rich. Jet kits frequently go up a size on the pilot to make the bike subjectively easier to start. It starts easy, but once the motor warms up, it's too fat and the idle rpm drops.

On the KLX110, the air screw is a tamper resistant triangle shaped screw that's recessed so you can't grab it with pliers. Not sure if the 140 is the same way, but if so you can use a dremel to cut a slot into the head so you can spin it with a regular screwdriver. Sounds like you need to lean your idle a bit, or turn out the air screw. Start with 1/4 turn, wait a few seconds, and adjust it until the idle rpm is the highest, then reset the throttle stop/idle adjust screw to the desired rpm.

Thanks, the air screw has a D shaped head that is recessed. I ordered the tool which should be here this week and I'll give it a shot.

I got the D tool in and I got it adjusted. I had to turn the air screw out quite a bit to get the idle at the highest point then adjusted the idle down. It seems to run good now. Is there a way to tell if I adjusted it to too lean?

One way to tell is if it pops on decel or the exhaust exit is turning white, same with the spark plug, sounds like you got it sorted out though.