I have a 9 year old Stihl 025 that has been a workhorse for me. I have never laid a wrench on the engine with the exception of air filters and spark plugs. This saw likely has hundreds of hours on it, but it still has plenty of compression and with a sharp chain and clean bar, cuts like an animal. Recent problem has been with seems to be a fuel puddling problem. When I get the saw hot, then set it down idling for any more than 10 seconds, I get an off-idle hesitation that feels like the saw is loading up. I get a little puff of black smoke out the exhaust if I can get it off idle without stalling. If it does stall, it fires back up easily. My experience with 2 strokes tells me that fuel has accumulated in the crankcase, and when the throttle is opened, the fuel is sucked through the ports into the combustion chamber and I get a momentary rich mixture. Outboards have a check valve in the crankcase to prevent this, but I don't think the saw does. Has anyone else had this problem with a Stihl saw? Any maintenance I may have missed that caused it?