I have an Exmark Lazer CT 52" cut with a Vanguard 18 hp motor. I bought it new in may of 2005. At the end of 2005, I was having trouble with the engine not having enough power to start the mower deck. I would start the engine, let the engine warm up, charge the throttle half way, engage the mower deck and the engine would die. This happened in maybe 2 instances, then went away. I've mowed probably 5 or 6 times this spring with no problems, then it started to happen again. The engine sputters, spits out black smoke when starting. The black smoke goes away after a few seconds. The engine is not running smoothly, doing a lot of chugging. As soon as I engage the mowing deck the engine dies. Any ideas before I tear into it?