help with summary on how to test compression

1048 Views 7 Replies 8 Participants Last post by Polaris-Man, Feb 6, 2002

sportster64

Discussion Starter · Jan 30, 2002

I've been readin' lots of posts on compression checking. CAn someone answer all of these at once: 1) Should engine be hot or cold ? 2)Should you hold the throttle open ? 3) Should you remove all plugs or just the plug from the cylinder you are testing(one at a time and replace) ? 4) I have also heard that you should keep the plugs grounded to prevent possible damage to the CDI box ?

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hotrod

· #2 · Jan 30, 2002

This is MY opinion and the way Ive successfulluy done it for years. Cold engine, Key and kill switch off, All plugs out. Throttle wide open and pull as many times as the Guage wont go up any more. Usually under five pulls per Cyl.

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Bman

· #3 · Jan 30, 2002

I agree with Hotrod but would also add that you pull equal number of pulls/cylinder. I never bother with the throttle wide open but don't see how that would hurt. Just make sure you are consistent from cylinder to cylinder.

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I think.... therefore I sled
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Rancid

· #4 · Feb 4, 2002

Well i was thinking about trading in an old sled last fall and took it to a dealer for an apprasial. the shop guys came out and when he tested it for compression he took out both plugs put the tester in one cyclinder and pulled it 5 times and took an average then he did it to the other one the same way. he said that i had low compression ( 100 psi ) but i still dont know what it was supposed to be . but he did say that unless one cyclinder differs from the other by more than 15 psi your OK

2002 ZL 800 EFI SS

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gigerous

· #5 · Feb 5, 2002

Generally. Under 100 PSI isnt all that great. Actually its borderline. Around 100-130 is great. More than that is awesome. 245 PSI. A guy that races his machine has that, is outrageous. A little too much for me.

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erick

· #6 · Feb 5, 2002

Hmm, I have never checked the compression on my sled. I am curious as to what it is. Hmm...

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xlt

· #7 · Feb 6, 2002

This is what the guys at Polaris told me. Take all the plugs out. Put the tester in. Hold the throttle wide open and pull 3 times. And do that for all the cylinders.

Ride Polaris!

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