Fish,
Interesting that Stihl came out with a liquid to help resolve sticky valve problems in their 4-mix engines. Seems like an admission that the engine is prone to valve stem carbon buildup. I found a Stihl service bulletin on the liquid that says to put the piston on valve overlap where both valves are open at the same time and then fill the cylinder with the liquid and let it soak for an hour. I assume this will also coat the valves, stems and guides of both partially open valves and hopefully free them up. Thanks for the heads up on this liquid as it's certainly worth trying before tearing into the engine. Also interesting is the fact that there is a short time when both valves are open as I found in my analysis of the valve working sequence.
I am now away from home and will not be back to work on the blower until late this week or on the weekend. There are Stihl dealers where I'm at now so I'll try to pick up a bottle of the "magic liquid" so I'll have it when I get back. Let's hope the problem is no more serious than a carbonized hung up valve.
I'll post again as soon as I get back to work on the blower.
Glen
