blew motor.. but why. Pics included

[sony224422]

Okay, so last summer i did a top end kit rebuild from SBT. I broke it in like you would a new engine, and everything was fine. Then I ran premix in it ontop of the oil pump still being in there, and it ran fine, didn't foul plugs or anything, just smoked alot.

The first time i ran it without premix, i toasted a cylinder. Its the one towards the rear (pto). I opened it up, and one cylinder had a greyish sludge in it, the other was perfect. I took a compression test before, and it gave about 40 psi in the bad cylinder and 120 in the good one. When i rebuilt the motor, i had around 120 in each if i recall correctly.

So, when i was pulling it out, i was looking for possible issues, and i found that the two lines on the Rave valves were broken after the tee in the line where it goes into the black box, was broken

I also noticed that the little black tube thats about 6 inches coming off the motor going into this check valve was ripped out compeletly, almost the whole length. What is this, and could it have caused my problems? I looked and the oil lines are intact still.. no oil leaking out of the little lines coming off the pump. unless maybe the jet in the carb is clogged.. i never thought to check. But heres the little black tube im talking about

here are some pics of the engine when i opened it up back in sept. i put it back together for the winter without fixing it and now im back to tracking down the problem so i can fix it again.

head top piece thing

you can see the grey goup im talking about.. what is it and what caused it? Did the broken vacuum line cause it to lean out and bake the ring into the piston? does it look like it lost oil in that cylinder?

 

[sony224422]

forgot to mention, the engine still turns over freely and easily, and it still ran.. sorta haha, enough to get back to the dock, so i don't tthink the crank or rods were damanged.

 

[PWCdoc]

I'd say that tube that is not connected to the check valve is the culprit. That line is what supplies the pressure to activate your powervalves and is supplied via pressure in the cases. When the line came off it essentially leaned out the rear cylinder and toasted the cylinder. The additional premix you were running helped to compensate for the lack of lube but when you went to injection only there was not enough oil to prevent damage.

 

[ski-d00]

I agree with doc. by the look of your head, both cylinders were smokin hot! I think the grey sludge is unburned fuel/oil mixture(remember it won't burn much without compression) mixed with aluminum dust from your piston or head degradating from the melt down.

you should watch plugs very closely after top end work, they should be very black and possibly foul when you are running twice the oil with no more than half throttle.

I'll be curious to see how purple your rods are from the heat, post pics if you can.

 

[sony224422]

will do. tearing it down tonight. i will take lots of pics. does it look like a new motor is in order or if the rods aren't too bad, i can reuse? i was gunna get the top end kit again haha, i think that line musta broken when i took it out the first time i am def gunna keep the oil injection and run premix when its fixed.. i'd rather foul plugs than blow the engine. I still have the plugs, i will post pics of them. They are black.. seemed to be ok. I am lucky because i ran it about a minute after it bogged down and shut off.. hopefully not too much damaged occured.

 

[sony224422]

oyyy. looks like its a little worse than i thought. Piston is compeletly destoryed.. looks like the other one wasn't far behind, though the wall and piston look okay. the rings are still loose on the piston and look to be okay on the front cylinder.

Not so much for the rear cylinder..

so, is it possible this caused it?

and where should i go from here? Cylinders look okay, i think i might be able to save the bad one with a hone?

and heres the rod

not discolored actually.. looks good, all the bearings look fresh and okay, nothing burned up or melted down low.


more pictures if anyone feels like looking at http://s11.photobucket.com/albums/a200/sony224422/jetski/

theres pics of the rave valves and such in there.

 

[ultramaxracing05]

when you get your new parts always make sure you achieve the right piston cylinder clearance, and ring end gap. here's a sight for WSM Pistons dirt cheap and free shipping beats the other stores. i got a set of pistons and new sleen for 63 for piston each and like 64 for sleeve, seadoo-partd.com

 

[ultramaxracing05]

seadoo-parts.com sorry

 

[sony224422]

sbt offers the whole top end kit for $500.. new rings pistons head and all the gaskets.

 

[glenwhitt]

piston color and condition

Any thoughs on this one. I have another thread on this at;

http://www.seadooforum.com/showthread.php?t=14330

Top end is 3 hours old and lower end is 23 hours old. More pics at other thread also. Thanks guys

 

[PWCdoc]

sbt offers the whole top end kit for $500.. new rings pistons head and all the gaskets.

I'll rebuild his top end for him for that price. But I'll use the better Pro-X pistons instead.

 

[glenwhitt]

PWCdoc and Pro-X pistons

Any truth to what heard on the Pro-X pistons, that they were lighter and are more sensitive to heat and have a higher rate of seizers?

 

[glenwhitt]

PWCdoc

One more thing doc, what do you think about the color of my pistons two post up? Does this tell you anything? The one with less black/carbon was the one with the best plug color and the one that did not loose 5psi compression after the first three hours. Thanks !

 

[sony224422]

You think I'll be ok with a rebuild?