i have just bought a yamaha 125 dt, and its my first 2 stoke bike, it seemed to run fine until i put new fuel in it. I put 125ml of 2 stroke oil into 4 liters of petrol and the bike seems to be back fireing, spluttering and conking out a lot, when i came back to start the bike it wouldn't start for me? any help or tips would be great full. thanks