1999 rm125 jumping out of gear!

[psaila]

hi guys my 99 rm is jumping out of 2nd/3rd gear when under load, only had the bike a week looks like ive been done! anyway is there any pointers you could give me on where to start? is there anything i can check before splitting the case?
i am prepared to give anything a go but have never delt with gearbox probs before!

thanks daz

 

[whenfoxforks-ruled]

Some of the dogs or cogs in the tranny are raked over and not holding the 2 gears together,it should make better sense once you have it open,good luck