I need help with my rm 125 issue!!!

I got a rm 125 2 stoke 1999 Was riding my bike today and it was running fine but black oil was dripping out the exhaust i dont know if this is normal or not i put it up against the wall while it was running to let it warm the gear box oil up because i was going to replace it then i revved it and it just bogged out now it wont start it stated after about 10 kicks and bogged out start away and now just wont start so i changed the air filter and i changed the gear box oil and it still wont start any ideas i left a little of the old petrol mix in there which was sitting for 3/4 years in the bike as it was not started for 3/4 years but was only a tiny and was running sound and put about 3 lieters of new petrol mix in was a little rich on 2 stoke about 36-1/ 38-1 its ment to be 32-1 but i dont think that matters does it dont know if the carb is dirty or whats going on got any ideas i bought the bike 2 days ago and have done nothing to it it was running fine till this happend i do not know if the fuel and air mix was right as when it was ideling turnt on not in gear it kept cutting out so i had to tighten it in but it did not need tightening before but it did today when i started it up help please this is my first 2 stroke bike??