checking engine compression

[gnu2this]

Would someone mind posting a link or describing the proper way to check engine compression? I have the manuals that rudi suggests but I have not found a step by step "how-to." I bought a compression gage at auto zone but I'm not sure how to use it. Can I just take the #1 spark plug out and screw in the gage and then hit the starter or do I need to use a hand crank and turn 1/4 turn at a time? Thanks!

[Matt Kirsch]

There's a link to a compression test FAQ in a thread of mine below, "115psi compression and still gutless" or something like that.

Taking compression readings is hardly rocket science, and is pretty much like you said: Take out the spark plug, screw in the compression gauge, and hit the starter button. The FAQ recommends 4 compression strokes to get a good reading, but then goes on to say you should crank until you get a stable reading.

Take a reading on each cylinder.

Of course, you do NOT want the engine to start, so hit the kill switch and/or remove the coil wire.

[Larry Barb Dotson]

I believe the correct way is to removee all spark plugs and crank until max. compression is achieved, usually about 4 compression strokes. No
worry that the engine will start without any spark plugs.

Larry D.

[magnumpi]

To play it safe, I'd only unscrew one plug at a time. In the automotive world, there's always the chance that you can blow out the head gasket between cylinders if there's a slight warp to the head or some head bolts are not uniformly torqued.

[John *.?-!.* cub owner]

Also make sure the throttle is open, and most accurate results are obtained with the engine warm.