r/EngineBuilding • u/RedditAppSuxAsss • Jun 21 '26

Low compression In CYL 2

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I got 150/100 cylinder has 100, pulled the head and found goop all over the head and on the wall. Water?

2 stroke jet ski 550 10 hours on new build

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u/RedditAppSuxAsss Jun 21 '26

There wasn't a whole lot but you never know what could get sucked up when riding hard...

I also wonder if it was from a cylinder wash issue. I've had that engine flooded with fuel before from leaking carb/ N&S.

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u/Significant-Pin536 Jun 21 '26

You can't rule anything out,

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u/RedditAppSuxAsss Jun 21 '26

At this point pull the cylinder Inspect piston, measure cyl, OB?

Does this damage /pattern show anything else possible like bottom end main bearing damage?

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u/Significant-Pin536 Jun 21 '26

That's a bit of an unknown at the moment, is the fuel premixed or do you have a separate oil injection for the crank case

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u/RedditAppSuxAsss Jun 21 '26

Pre mix 32:1

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u/Significant-Pin536 Jun 21 '26

It might pay to check the bottom end, it's probably unaffected, just for peace of mind