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How do I adjust the valves on my Craftsman model 917.271832 lawn tractor with a Briggs and Stratton engine?

It is a Briggs and Stratton engine model 461707-0147-E1, 21 hp. The engine is hard to start. It will hardly turn over if at all. Are the valves adjustable and what is the process? I was told this is what is wrong with it.

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Craftsman , Lawn Tractors , Lawn & Garden
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Manage My Life
To adjust the valves on the engine, remove the screws in the valve covers and remove the valve covers. Remove the spark plugs from the engine.

Put a clean small, but long, screwdriver into the spark plug opening so you can tell when the piston is at the top of the stroke.

Rotate the flywheel until the piston is at top dead center and neither valve has any pressure on them. The push rods will be loose in the rocker arm. If one push rod has pressure on it, rotate the engine again and when it comes back to the top of the stroke neither push rod should have any pressure.

Use a feeler gauge to measure the clearance between the end of the push rod and the rocker arm.

The clearance on the intake valve should be .003.- 005 inches. The clearance on the exhaust valve should be .005-.007 inches.

If adjustment is required, loosen the allen set screw in the center of the nut on the rocker arm and adjust the nut to obtain the proper clearance.

The intake push rod is aluminum, and the exhaust push rod is steel. This will help you determine which valve is which.

You could also have a worn lobe on the camshaft inside the engine. To test for this rotate the engine by hand and watch the rocker arms move. You should have about the same amount of lift on each rocker arm. If one or more rocker arms is barely moving, the lobe on the camshaft is worn.
by Manage My Life
July 9th, 2009
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