I have a seadoo gsx 800 1997, its been running well and have had no real problems (since carbs rebuild). I borrowed a compression tester off of a friend just to see what compression the cylinders were, they are both about 75 psi, from reading on here i see it should be around 140. its done 100hrs and is running fine, does nearly 60mph, accelerates good and starts up fine (and tows inflatables) my question is should i investigate the low compression or carry on as i am, thanks
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compression low but running fine ?
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BMANN06
Well-Known Member
If it ain't broke don't fix it!
That's an interesting reading, I would suspect the gauge or the test as you would be getting alot of "Blow By" with this low of compression and certainly wouldn't be able to hit 60mph.
Blow-by is on the "power/ignition stroke" where gases force the pistion down but "blow by" occurs when gasses get around the pistion rings causing a loss of power.
The other thing could have been the test, when doing a compression test always ... always ... always get the engine to operating temperature. Then pull a plug and all plug wires and start to test compression.
Hope this helps.
That's an interesting reading, I would suspect the gauge or the test as you would be getting alot of "Blow By" with this low of compression and certainly wouldn't be able to hit 60mph.
Blow-by is on the "power/ignition stroke" where gases force the pistion down but "blow by" occurs when gasses get around the pistion rings causing a loss of power.
The other thing could have been the test, when doing a compression test always ... always ... always get the engine to operating temperature. Then pull a plug and all plug wires and start to test compression.
Hope this helps.
Dr Honda
Well-Known Member
Yup... that gauge is bad. A rotax engine isn't going to run in the water (at all) if the compression is less than 100 psi. At 120 psi... you may get it to start, but will have a bad low RPM durability.
If the compression is very low, but is still running... the engine will eat it self. The blow-by will overheat the piston skirts, and burn away the oil that should be lubing it.
Just some random thoughts from a mad man.
If the compression is very low, but is still running... the engine will eat it self. The blow-by will overheat the piston skirts, and burn away the oil that should be lubing it.
Just some random thoughts from a mad man.
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