hey. i have a 1980 skidoo citation 3500. at first i had problems starting the sled so i changed the spark plug and it fired right up. had it idleing for a while. after around the 5th start, i had to change the spark plug again. I was out riding for around 30 min one day and it started to die on me and wouldnt start back up. i noticed BLACK (oil?) all around the square hole in the plastic cover over the motor (near the spark plug). spark plug is tight. anyone with any suggestions? please help! theres snow and i want to go riding!