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Compression Release Valve Makes Mower Easier To Start
Merle Black, Valencia, Pa.: "Anyone who owns a Gravely walk-behind, rope-start mower knows how hard it is to start them. The problem is that you're pulling against compression inside the engine which makes it hard to turn over. I solved the problem by installing a compression release valve made by Stihl Co. The company equips its bigger chain saw models with these valves to make them easier to start.
  "To install the valve I drill a 3/8-in. dia. hole above the exhaust valve and all the way through the head, then use a metric tap to make threads in the hole and screw the valve in. Pushing a button on the valve releases pressure in the cylinder and makes the engine easier to turn over when you pull on the rope. Once the engine starts, the valve automatically closes.
  "The hole above the exhaust valve prevents any change in the mixture of fuel as it comes in from the intake side of the carburetor. Stihl doesn't keep these valves in stock, but you can order them from the company. Before installing the valve I first used a grinder to remove the fins that cool the engine, providing me with room to drill the hole."

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1999 - Volume #23, Issue #5