Blade Spins Freely When Running And After Shut Down.....cluch?

The most probable -- and easiest to fix -- cause of chain rotation while the chainsaw engine idles is a poorly adjusted idle setting on the carburetor. The result is that too much fuel is delivered to the combustion chamber when the throttle is released, and the engine doesn't really slow. Correcting the problem requires adjusting the idle screw -- usually marked "I" --on the carburetor. The idle screw usually is near or behind the air filter. Adjust the screw to restrict fuel delivery by turning it clockwise with a screwdriver until the chain stops turning. The saw must be running when you do this. Turn the screw slightly counterclockwise if the engine starts to sputter.

You may notice that in addition to the chain not stopping the chainsaw has other symptoms, such as smoking and the engine racing, which can be caused by a rich fuel mixture. Achieving better performance from the chainsaw may be possible by adjusting its low-speed carburetor screw -- usually marked "L" or "LA" -- to create a slightly leaner fuel mixture. In order to do that, warm up the chainsaw's engine, and then, with the engine running, turn the low-speed carburetor screw clockwise one-quarter turn or less. A dirty air filter also can be responsible for an overly rich fuel mixture. Take out the air filter, and, if it's salvageable, clean it with compressed air or by washing it with soapy water. Otherwise, replace the air filter.

If the chainsaw's performance doesn't seem to be an issue, you can narrow the possible causes of the chain's problem to one: the clutch. A chainsaw is equipped with a centrifugal clutch, which is designed to engage the chain sprocket and the motor only when the throttle is engaged. The centrifugal force generated when the engine spins forces the clutch shoes out to contact the clutch drum; when the engine stops, a set of springs retracts the shoes. When the clutch doesn't retract, the chain continues to spin, and the cause is either that the shoes are stuck or the springs are broken.

The process of servicing the clutch requires the removal of the chain sprocket, which can be tricky because the screw holding it is in its center, and the screw can't be turned without turning the sprocket. The remedy is to remove the spark plug and stuff a length of nylon rope into the piston cylinder to prevent the piston and engine flywheel from turning. After removing the sprocket, you may be able to get the brake shoes unstuck or replace the broken springs. In most cases, however, the most effective repair is simply to unscrew the brake shoes from the flywheel and replace them.

Thanks