my fully stock 700 has just recently been messing up. It has always had a slow start to it, but recently acted as if the battery was going dead. It would start when jumped, and would start after it was warm. Now, however it will not start at all by the switch. It turns the starter but acts as if the compression is to high to turn the motor over. it will start when dragged. when its cold, it will blow black smoke as if it's flooding itself. once warm, it runs great, but still has to be pull started. could it be valves, decompression switch, Cam?