KTM 125sx pilot jet question

Read thru Spanky's Jetting guide at the top of the 2 Stroke Forum. Follow the guide and get it jetted correctly. Worth the time and you'll understand your bike much better afterwards. Make 1 change at a time and test. Do the changes in the order the guide tells you and you will be good.

Give me the altitude and approximate temperature where you will be riding and I can give you the baseline jetting information from KTM.

Assuming Fahrenheit this should get you started.
(-2-20 degrees F, 0-1000 ft)
Air Screw: .75 turns out
Idle Jet: 52
Needle: R1468D
Clip Position: 4 (from top)
Main Jet: 168

IMO, err on the side of rich and get it running right before you complicate things with mods. This way the changes will be easier to predict.

Don't pay any attention to the way it runs on the stand. Take it out and run it for 5 minutes or so under load and you'll be able to start tuning. Follow the jetting guide exactly and thoroughly. If you're worried about it being too lean from the get go, drop the needle clip a notch or two and turn in the air screw a half turn. If it's dripping spooge I doubt it's dangerously lean.

Also, it is possible to over oil air filters. Not common, but possible. If you wrap the filter in paper towels and squeeze it out well you'll know you have just the right amount of oil on it.

Running it on the stand won't make it lean.

All good advice here guys, but here is my take on the situation as an old guy who has been running 2 strokes since 1974:
1) It is an 8 year old used bike new to you. Leak test the engine to make sure the case, gaskets and crank seals are not leaking. You do this by plugging the intake with a bung at the carb mount and with an expanding rubber plug in the exhaust hole. You pump the engine up with 7psi and see if it holds it. If the engine is leaking air you will never get jetting right.
2) Drain the tank and put new gas/oil mix in. Buy an excellent brand of 2 stroke oil and stick with it. Mix it as to the instructions which are 50:1 for your bike. Sticking to known good components and manufacturer's procedures makes things MUCH MUCH easier to troubleshoot.
3) Follow the KTM manual for jetting for your altitude and temperature. These recommendations are on the rich side but will work and are safe and will get you running safely IF there are no case leaks. You checked this in #1) right?
4) Run it, warm it up gently, look for problems and leaks, solve them. Stick a new plug in it and run it up through the gears. Shut it off and pull the clutch at top speed, then pull the plug and look at it. This is called a plug chop. Learn to read the plug. This will tell you if the main jet is right. You may be able to lean it out a size or two for better performance.
5) Jetting pilot (idle) and needle are bit complicated to explain here but well worth doing for crisp response and engine life. Read up on it and learn it.
6) NOW stick your Doma pipe on. Jet rich a jet or two if you want and plug chop it again. You will be able to read if you are lean or rich on the main.

Make all mods one at a time and only to a known well working engine. Sticking to as close to manufacturer's specs assures the longest engine life and easiest trouble shooting. Stock these engines work well and long, learn to keep them running stock before you start experimenting, and then just change one thing at a time.

Here is a leak tester and a plug reading chart: