I've always felt that a high revving 125 needed more oil than 40:1
There is also benefit of better ring seal and consequently more compression with more oil.
If I were you, I would try a bit more oil in the mix (32:1-20:1). Simply changing your ratio will lean things out a bit, but then you need to jet all the circuits proper for that choosen ratio.
Also remember that a little spooge is not always a bad thing. Even with the bike jetted spot on for hard riding, you can see spooge just from riding a bit less aggressive for a time.
If you have had lots of residue coming out of your pipe, you may want to consider having the pipe cleaned at a radiator shop. Old spooge can confuse you into thinking you still need jet work when you may be just right. Choice of oil brand also makes a difference on the residue you may see.
Read Eric Gorr's instructions on how to jet proper.