Top End Rebuild Advice

[aquaman222]

I posted my problems with my 1996 XP before, but I’m recapping it all here since I did just pull the head. Basically my ski bogged down with no signs of problems on the lake. It was running very strong, then it would not start.

When I got home I tried to start the ski and it fired right up then had a loud backfire and was difficult to start.

I have recently cleaned the carbs, replaced fuel lines, plugs and rave valves. My valves look real dirty even after only a few rides.

I checked compression and found the Mag cylinder to be at 145 and the PTO and basically nothing. Perhaps 20. I pulled the head and quickly discovered the PTO piston was fried. It looks like the rings broke and got into the head or perhaps the previous broken rave valves that I replaced had some chips that dropped into the head. Both of my old valves broke at the stems and if anything got in the head it was minimal. It could account for most of the valve pieces.

From the pics you can see how bad the PTO piston was. My head is also probably toast. The Mag cylinder is covered in carbon, but appears to have no damage.
I’m replacing the entire top-end, but I really want to make sure I get to the cause of this so the problem does not repeat.

I’m also going to rebuild the carbs and am considering going to premix.

One final note. I do not know what type of oil the previous owner was using. I drained most out of the tank and replaced with Quicksilver full syntetic.

I don’t think anything got into the bottom end of the motor but I stuck a tube down in the bottom end and vacuumed out what I could and found nothing. No signs of metal.

Any advice or comments would be greatly appreciated.

 

[Dr Honda]

Sorry for the meltdown.

OK... it could have been a few things that caused it. 2 of them you touched on. 1) Not knowing what oil they were using. 2) Busted RAVE.

With that said... the Quicksilver you put in... was it the PWC oil? Quicksilver makes a full synth that is a TC-w3 oil. (outboard engine) That oil will not suport the HP of a Seadoo 800 engine.

One other thing that could have caused the problem is a case leak. Even though the engine only has 100 hr's on it... it's still 15 years old. The crank seals, and bearings could be going bad. That would lead to a lean run. If you want to make sure it doesn't happen again... do a leak down test.

The last picture is too grainy/blurry to get a good look at the piston skirt, but from the damage on the first piston... this was not an "Oil" issue. The crown of the 800 pistons is very thin... and it looks like the ring shattered, and took out the top end. Knowing that... why would you want to go to pre-mix?

Good luck with the rebuild.

 

[aquaman222]

I put in the full synthetic PWC blend of Quicksilver. I'm pretty certain it is the right oil. I'll take a pic of the package tonight. The sleeves feel very smooth. No grooves or nics in them. What about all the carbon build up on the mag piston head?

Also, I'm obviously a rookie and I've never heard of a leak down test. Any advice on that would be good.

The premix is just a precaution for me. I don't want to get this all back together and have a problem with that. Could a carb issue cause the rings to fail? Like running to lean or rich? What would cause rings to break up like that?

 

[Dr Honda]

A very lean mix will cause it to over heat the rings... and if you melt the piston crown (at the edge) the ring will break free.

Looking at the piston wash on the MAG piston... it could have been a little lean. (but on the edge of OK) The cool, incoming fuel should keep the piston crown clean by the ports.

This pic is a little exaggerated... but you can get a visual on it.

 

[aquaman222]

Any advice on a where to purchase a rebuild kit for the top end and my carbs? I've heard different quality comments on both.

 

[aquaman222]

Also, I was looking for a good source for a new top end rebuild kit. Do I need to replace the piston cases if they are smooth? Will a new piston simply drop into my old case without any additional shop work? I'm also looking for a good carb rebuild kit. Any suggestions?

 

[jerrygena]

Hi, i sent my jugs out to full bore online, took about 2 weeks, i sent them new rave valves to cut, total was $315, now i just got to get it to start..........................

 

[Dr Honda]

if the cylinders are smooth... then you can give them a quick hone, and replace the pistons.

Before sending them out for machine work. You may want to see if there is a local shop that can do it.

 

[aquaman222]

So am I better off buying the top end swap out from SBT? I'm not sure what you mean by hone? Does a new piston have to be matched to the cylinders? That is what I'm understanding.

 

[92rslt1]

Are the cylinders in that plated? If so I wouldnt advise honing them too much. Judging by the piston carnage that needs a bore. It looks like you were running into some detonation.. It was definetly lean. Like others said possible air leak. Did you use new gaskets on the carbs when you cleaned them? take your jugs to a reputable shop and have them measure them and inspect the bores. If needed they will order the proper pistons and have them set up for you ready to drop in when u pick them up. Or you can get the kits online, like sbt offers.

 

[Rampage]

Your piston looks just like mine did. I found my last chance filter in my carb completley plugged on that cylinder. I just got WSM piston and ring kit on mine

 

[ocod]

^how do you repair/replace mag dome? Mine is like your picture and I read where to sand it down or replace it??

 

[Rampage]

I used a dremmel with a stone that worked ok, but I ended up just getting a used one and slapping it on. I didnt hone my jugs out or anything. After it was complete I did a comression check and I was 150 per cylinder. I know I should have done a quick finish on them but didnt have one and was riding that weekend with a group. Ski is still running strong.

 

[Dr Honda]

So am I better off buying the top end swap out from SBT? I'm not sure what you mean by hone? Does a new piston have to be matched to the cylinders? That is what I'm understanding.

If you don't know what a cyl hone is... then it's best to take it to a shop to do the cyl work. (Not being harsh, just want to see you with a good engine) You can still do the install of the new parts. And yes... the STB top end swap is a good kit... and they will get you parts fast.

YES... the piston needs to be matched, but since you can see the crown of the other side... you can ID the piston, and just get a replacement.

Are the cylinders in that plated?

No... seadoo does not plate their Cyl's.

^how do you repair/replace mag dome? Mine is like your picture and I read where to sand it down or replace it??

Sandpaper works well. If you aren't building a race engine... just take the sharp edges off, and run the squash gap on the big side of tolerance.