Hi
I have always had 2 stroke mx bikes, the last was an 07 honda 125 which I ran at 32:1 fully synthetic and it was fine but I know what you are saying, years ago I always ran all my 2 strokes on 40:1 including 125s and 250s and that was the norm, had a spell away from mx and when re-started it had all changed.
We ran 40:1 to help stop them choking at lower revs but I guess with modern synthetic oils it helps against that, certainly never had a problem with the last Honda.
Try using good quality fully synth at 36:1 and see how it goes, I guess you could go to 40:1 if it gets choked up but keep an eye on the jetting and plugs so you know its not running too lean.
My oldest son races but he made the moved to 4 strokes back in 2004 and now has an 09 yam 450, good powerfull bikes but you cant beat the sound of a 2 stroke being rid hard
Tim