my 1987 atc200x went down while i was riding it i was barely moving when it did it i took it apart and the oil pump chain had came off the oil pump sprocket slid out and the pump broke letting the chain fly loose luckly nothing but pump and chain was hurt i replaced pump chain and sprocket but it back together and added oil to engine but when i tryed to start it it just backfires my thought was it some how jumped time could this be the problem anyone have any idea's what this could be or how to fix it let me know.
