compression test

[jamesandhay]

Hi,

My jet ski runs fine but i wanted to know what psi each cylinder should be?

They are both measuring 127 each. i heard they should be at 155? if this is the case what could it mean if mine is so low and how can i improve it? will it affect performance.

oh forgot to say i now have a 97' gtx 3 seater.

james

 

[glenwhitt]

should be ok

at 127 in each you are fine. if you have more than 10% diff between them then that is cause for concern i hear.

 

[kustomkarl]

Here is some information on compression tests.
To test compression, remove both spark plugs. Place spark plug caps on the plug cap studs near the cylinder head to ground the empty caps. This completes the circuit of the ignition electrical system and prevents any electrical problems from the caps being un grounded. Using the correct adapter for the threaded end of the tester,( same length of the spark plug threads length)screw in the tester in one plug hole. Hold the throttle wide open. Push the start button. Watch the compression gauge, when it peaks out at the most compression, let go the start button. Read the psi number. I would do it 3 times to be sure it is accurate. Check both cylinders the same way. The ideal compression is 150 psi per cylinder. If it is less, it's not a problem as long as they are close to being the same. If the psi is less than 90 it might need be time for a tear down and a rebuild. If the psi in 1 cylinder is say 140 psi and the other is 80 psi you need to tear down and repair. This difference is a lot then there is a problem. I hope this helps you.

Karl

 

[custompartsguy]

:agree: Plus many dealers will tell you 155....but you must understand it is not a brand new engine that has not been run yet, as long as they are close to each other as Karl stated you are fine

 

[glenwhitt]

Wot

ya. not having it WOT during the test will cause some low readings. Made that mistake once after putting on a few hours on a new top end. came back did test with throttle closed and scared to death i had losta bunch of compression. Turns out after the rings seated i have gone up a few pounds, when testing WOT.

 

[Sprocket62]

Thanks, kustomkarl, I'm getting ready to testride 2 1997 XPs and I wanted to do a compression test when I do. I knew I needed to ground the plug wires, wasn't sure how on a seadoo.

 

[kustomkarl]

If you have any other questions let us know, we're here for ya...


Karl