I still stick to my original post of painting it. Mentioned that it will get worst over the winter until the snow melts. So take the pipe off now and prep and paint.Come on guys, This is a tech thread.No need to derail it.
If you are dead set on getting a new pipe and want an FMF, I will share my experiences with these pipes and jetting over the years. I have ran FMF pipes over the course of my 101 years of riding and I find that the only real thing that I needed to do is move the clip on the needle one position. I have ran a fatter main one size on occasion but is to handle holding the throttle in the wide open range for long periods of time when I thought I was a fast young gun
I never had a 125 2 stroke but I did do the same thing for my son's YZ85 and all the 250 and 500 2 strokes I owned over the many years. A bike is pretty good jetted wise between 0 - 5000 feet elevation, so if you are jetted good between these elevations, you should be fine. Temperature does play a part, but not really too much unless you are racing on a track and or desert and need the ultimate jetting. On my 03 YZ250, I have a FMF Fatty and Titanium shorty. I dropped the needle one clip and went one up on the main. I ride mainly between 2000 - 5000 feet and the bike barks with no hesitations. When getting up in the upper elevations 5000+, I notice a slight change, but since I am just play riding and it is normally just for the day, I do not bother changing the jetting since the bike still runs good.Hope this helps, but as I said before, you mentioned that you are still learning and will be dropping the bike a few times. Save the $100+ on a new pipe and paint the stocker and run it since your bike is running in top shape now. Go take the pipe off and warm it up and prep and paint it for when the season comes back around.
CDA Out!
-BIG DAN