hello i need some help i have a 1998 polaris 500 sportsman it worked good up until tonight i was driving and the motor just died sounded pretty rough along with a cloud of smoke however the buggy still has lots of compression like usual it has a nice blue spark and is gettin gas through the carburator timing chain is tight and it has oil in the oil filter black but not gritty it turns over  . oil pump? i really hope somebody can help me this is my brothers buggy and he is not gonna be impressed with me haha so if u have had a similar problem could you please help me out thanks.