How to do a compression check

[hahnb13]

Looking to purchase a Force 120, 1997 model and want to check out compression. Please help. Thanks

 

[Silvertip]

Re: How to do a compression check

Buy or borrow a compression gauge at any store that sells auto accessories and parts.<br />Remove the plugs.<br />Ground each plug wire or pull the kill switch<br />Spin the engine over.<br />Read the compression. <br />Repeat for all cylinders<br />No more than 10% difference between readings is acceptable. Any cylinder less than 90# indicates a problem although a thorough decarbing re-test would be in order before forming an opinion on rebuild.

 

[hahnb13]

Re: How to do a compression check

Not sure about the ground each plug wire? How is that done? Also, if there is a kill switch, engage and then crank engine?

 

[Silvertip]

Re: How to do a compression check

You want the ignition disabled during the test as any fuel vapors expelled from the spark plug holes will tend to curl your eyebrows when the sparks from the plug wires ignite those vapors. Activating the kill switch disables the ignition, just like when you fall overboard (provided the lanyard is attached to you).

 

[eurolarva]

Re: How to do a compression check

Tie wires around the threads of the plugs and tie it to the metal on your motor or your negative battery lead. Another reason to to disable or ground the plugs is so that you dont fry out the ignition system.