I run the Motul at 80:1 in my trials bike, and would not really recommend running your Mx bike at over 50:1. I think that unless you are just putting around (like on a trials bike!!!) you will wear out your piston and rings far quicker than would be economic. With a trials bike the leaner oil mixtures are ok, but with a Mx bike, particularily a 125, you will be screaming for extended periods.
I have seen frequent dicussions on oil ratios with respect to trials bikes and some people run theirs on 100:1 with synthetic oil. I have not been that brave, and don't want the hassles of replacing piston and rings every few hours.
If you are having problems with lots of spooge, then find a decent long hill climb, and really clean out you motor and exhaust. There is a Tech Tip from a trials site, which helps to explain how to get rid of any excess oil in your exhaust system.
http://www.trials.com.au/techtips/plugs6.html
Remember this is for a trials bike, so forget about the 100:1 part!!