I've just recently sold my crf and got a 2012 GG 250 EC Racing and wondered if I could used some Motul 5100 10/40w oil in the gearbox. Reason is I have 10l of the stuff from my crf.
Yes, it will be fine.
I haven't run it personally and it wouldn't be my first choice of gearbox oil. Mostly just because it's relatively expensive, but you already have so use it.