Engine damage diagnosis 787

[robomatic12]

I can hear a knocking noise internally and the engine won't start so I pulled off the cylinder head and I found damage from metal going through the forward cylinder. I'm not sure what this was caused by, if it is detonation damage or something inside that let loose. The bore isn't very scratched up. I pulled the rave valve on that cylinder to see if it came apart but it looked normal. Also that piston doesn't come up as far as it should, leading me to believe the rod is bent. In the photo that is as high as the piston comes up. I've been using seadoo xps 2 synthetic oil.









Little piece of something embedded in the cylinder head


Other cylinder

 

[OhNoItsMe]

Kinda looks like a small piece of a piston ring if u take off the rave valve assembly u could get a look at the side of the piston w/o removing the cylinder

That's what I'd try next before removing the cylinder

Hope that helps

 

[Waterluvr]

That bad cylinder / piston has been steam cleaned in the picture you posted. -very likely the rod was bent in the process. Probably not a candidate for just a top end without thorough inspection of the crank and pressure testing the lower case.

 

[robomatic12]

How would a cylinder ingest water?

Did you see the little metalic piece in the photo? It has ribs on it, not sure if thats a telling sign of where it came from.

 

[Waterluvr]

How would a cylinder ingest water?

Did you see the little metalic piece in the photo? It has ribs on it, not sure if thats a telling sign of where it came from.

See the red arrows I placed on your photo on the area that looks like rust? The only ferrous metal in that portion of the engine is the cylinder sleeve and piston rings, the seal in that area looks like it let water in and steam back out depositing that iron staining in that area.

Who knows, loose head bolt or your compression could have been so low the blow by was cooking off the oil film on your pistons and it was seizing. There's a noticeable groove worn into the top of the cylinder where the piston rings reverse direction, I would venture a guess that engine compression was well past the point of needing the top end rebuilt.

 

[kicker]

Are those grey tempo fuel lines on there that I see?

Either way, those cylinders will have to come off to clean the bottom end, there will be debris in there. I think you will find your problem once you remove the cylinders.

 

[robomatic12]

Those are just for the pulse line to the fuel pumps. All other fuel line is proper marine spec hose. For some reason seadoo used the tempo hose only for the pulse line on the speedster.

I will have to pull the cylinder jugs off for closer inspection. I think I am going to get a sbt engine anyways. Thanks for all the great replies

 

[robomatic12]

Based on the PTO cylinder, how do the carb settings look? Both carbs were rebuilt with OEM needles/seats and OEM gasket kit with the correct pop off verified and all OEM needle settings. I'm just trying to make sure I won't run into the same issue with the new engine.