What do you guys think happened with this?

[uncle-buck]

Here are photos of portions of the engine of my '99 GP1200 less than 10 hours after a top-end rebuild.

What does it look like to you?

Thanks in advance for any comments.

[Technical Support]

Re: What do you guys think happened with this?

It looks like you need to keep tearing it down :)

[WATERCRAFTSERVICES]

Re: What do you guys think happened with this?

Hey uncle buck. Wow 10 hrs. Looks nasty. Looks like a ring broke and caused this. That would be my educated guess without seeing entire piston. I have seen this exact damage caused be a broken ring snagging a port and tearing everything up in the bore. Post the piston pics when available. Curious to know. Good luck.

[uncle-buck]

Re: What do you guys think happened with this?

I'll post more photos of the pistons and cylinders after I remove them in a few days. Since I have purchased an SBT engine, I don't plan to tear it completely down.

Before the top-end rebuild, the engine seized a few times and I didn't recognize or understand what was happening. I continued to ride and burned up the center piston. I was told that a diaphragm in the center carb got a dimple in it and leaned it out.

I took it for repair to an independent tech in Houston. He's a PWC racer and was supposed to be a good mechanic. He recommended and supposedly performed a top-end rebuild. But the engine never performed properly or had adequate compression after he worked it it. I returned it to him twice after he did the job (once for 7 weeks) to give him an opportunity to make good on his work. But he never did.

Here's a link to a previously posted thread with more background info. on this:

http://server1.sbtontheweb.com/forum...ead.php?t=3127

I'm not looking for a fix here - just trying to learn by understanding what happened. Thanks in advance for any insights.

[Technical Support]

Re: What do you guys think happened with this?

There's no point guessing until it's broken all the way down. It could be a number of things, but all we can see here is the aftermath, not the cause.

[SuzanGPR]

Re: What do you guys think happened with this?

My guess would be not enough oil to the engine. If you lean an engine out, detonation is going to happen. Have you checked your oil pump to see if it's working properly? Just my two cents. :)

[uncle-buck]

Re: What do you guys think happened with this?

OK, here are some photos of the center piston from my GP1200 engine. Thanks for any comments.

[Technical Support]

Re: What do you guys think happened with this?

That is not ring snag, detonation, water or lack of oil - it's debris. Check your wrist-pin and crank bearings for damage/missing rollers. Something passed through the engine.

[uncle-buck]

Re: What do you guys think happened with this?

The wrist pin bearings are fine. What's the best way to separate the crankshaft from the bottom half of the case? I've got the case halves separated, but the crankshaft seems to be stuck in the case.

[WATERCRAFTSERVICES]

Re: What do you guys think happened with this?

I agree. Not ring snag. But there was something floating around in the bore to cause this. Was there any foreigh material in the crankcase when you split it? To remove the crank,tap the ends with a rubber mallet. This should break it loose.Look close at all bearings. They may tell the story. I had a 701 once that had similar piston damage that the center crank bearing went out and spread debris around.

[dank]

Re: What do you guys think happened with this?

Also check the reed cage and the choke plate for a missing screw.

[Mpeavler1]

Re: What do you guys think happened with this?

Also ensure that the piston ring pin is not missing....I cannot tell from the pictures. Those are sometimes found missing out of their bosses and somewhere into the cylinders.

Mike

[Technical Support]

Re: What do you guys think happened with this?

Pins do come out, however that allows the ring(s) to rotate and snag.

[Bill O'Neal2]

Re: What do you guys think happened with this?

I've seen pins that came out.

[uncle-buck]

Re: What do you guys think happened with this?

There is no visible debris in the crank case, all rollers on the crank bearings look to be in good shape, all piston ring pins are intact, and all reed cage screws are intact.

The carbs were sent to Island Racing, and I'm sure Carl will let me know if he finds any screws missing from the choke plates.

However, given the general sloppiness of the work performed by the man who rebuilt the top-end, and his responses to various questions about the job, I believe it likely that something dropped into the intake on his watch. Keep in mind that after he rebuilt the engine:

I found an oil line wedged between the air box and the motor.
Cylinder compression was very low and uneven.
He told me to use the long adapter to re-check compression.
He said that compression readings may have been low because of the thickness of the base gasket he used.
(The list goes on, but you get the idea.)

Thanks for all of your responses and for trying to help. Have a good weekend.