Right - what I said.... sounds like your engine is running lean. Check for leaky line, etc... The only thing changing the number of washers does is change the compression ratio. Less washers = more compression. More compression = hotter motor and less tolerance to a poor fuel/air mix. Try changing your fuel/air mix - richen it up some after you check to make sure your lines are good and the muffler is tight. If it gets worse then you are incredible rich and locking the motor - lean it out (odds are your lean though). If that doesn't fix it then it's probably the glow plug.