Open heart surgery on the SL780

[hyoctane23]

Figured I would start a little post about my endeavor I took over. My ski had injested some water and I could not for the life of me get it started. My step dad and I were outside drinking some beer at the creek house when I looked over and noticed the ski was about 3/4 underwater. That was at about 2AM and we tried until about 4AM but no luck.

So I've torn down the motor and noticed a few things. First, the middle cylinder obiously had some sort of foreign object inside because the crown of the piston and the cylinder head are pitted. I ordered a complete topend rebuild kit that includes WSM pistons and all the gaskets.

I cracked the crank casing today and I have it sitting in some varsol cleaning up while I have the crank wrapped in a towel with a good layer of oil on it to keep it from rusting. All the bearings turn without problems and without a lot of noise so I think they are good. Rods are straight and don't have any up and down play, so I think the rods and crank are good.

I also took it upon myself to clean out the electrical box. Luckily all the wires are color coordinated so I pulled them all apart and cleaned the circuit board pretty well. I have a question though...On one of the coils, the plug wire seems to have pulled out some, not all the way, but about an eighth of an inch. I have no idea if that has been like that since day 1, but would it be OK you think if I just kind of pushed it back in?

I'll get some pictures up a little later. The hull is pretty damned stripped. About the only thing left inside is the gas and oil tank. Any sort of upgrades I should do while I have it all apart? I also think the pump bearings need to be replaced, and I'm going to do the fuel hoses and carbs while I'm in there...

[xlint89]

You should post this in the projects section. It would be great for newbies to see the progress you make and the ease of doing it. Post as many pics as possible please. Upgrades would be maybe some aftermarket reeds. The 780 is pretty much a strong engine as is with some good parts already used. Is yours the long jet pump, if not that would help. And a SS 6 vane stator for the pump would be nice too.

[hyoctane23]

I got in my WSM rebuild kit in today It appears to be a pretty good kit as it is packaged really well. All the gaskets andn bearings seem to be top notch.

I have one concern though. On one of the pistons, there is a small flaw on the top of the piston. It almost looks like a casting flaw. If you look on the first picture at about 8:00, you can see it. I can kind of scrape it with my fingernail so it isn't just discoloration. Would this turn into a hot spot? Should I contact WSM or the supplier and have the piston swapped out before something else catastrophic happens?

[rgard32]

wow..in that first closeup pic...it looks like a head of a nail in there LOL....it will prolly be fine thou...

[ph2ocraft]

I'd call them and see what they say. I know I wouldn't be happy installing that in my ride.
I guess that's why I go with OEM on the pistons??

[hyoctane23]

Should I contact WSM directly or the supplier who I bought the kit from? rgard32, you're almost right, it almost looks like the head of a small finishing nail, but its flat with the rest of the piston head.

[ZMANN]

I think WSM was the original OEM mfg for some of the fuji's

[rgard32]

i think it will be fine......cast pistons never look perfect...and if u dont run it lean u should be ok....in my opinion..

[xlint89]

If you decide to run it, I'd install it into the CEN. She seems to be the least hardest working of the 3.

[hyoctane23]

If you decide to run it, I'd install it into the CEN. She seems to be the least hardest working of the 3.

I was thinking that on my way to work, even though I should of been paying attention to the traffic LOL. Just shows how much I want to get my ski back and running. I've only been out on the water ONCE this entire season. Rather depressing if you ask me...

Couple of questions: I tried to find the info, but it's not to be found!

1. How can I check the oil pump once I get things put back together before finding out the hard way?

2. Is it pretty necessary that I rebuild my carbs if my ski was flooded? They were working great before, and still seemed to work fine when I was attempting to start my ski.

3. I think my bendix drive was sticking because when I would try to start the ski, it would catch for maybe a second, and the starter would just free spin. Would it be OK to soak it in some varsol to clean it out, and oil it back up? Any way to test it?

4. I think my pump bearings are toast because it is hard to turn the drive shaft, and when it does finally start to turn, it feels pretty gritty. Does this sound like I should invest in some new bearings and seals?

Thanks a bunch!! Oh, more pics later tonight when I get home from work.

[axgrider73]

So I've torn down the motor and noticed a few things. First, the middle cylinder obiously had some sort of foreign object inside because the crown of the piston and the cylinder head are pitted. ...

Can you post some pics of this piston. Sounds like it could have been detonation. If so, you will want to watch for this when you get back in the water.

IMO it would be foolish to rebuild the engine and not rebuild the carbs.

Just my 2 cents,

Rob

[hyoctane23]

I will post some pics when I get home from work today. I now agree that it would be foolish to not do anything to the carbs when I took all this time to rebuild the motor. I guess now I wonder if I can get the rebuild kits at a local auto supply store? Or if I just disassemble the carbs and clean everything out, would that be good if things still look nice?

[beerdart]

Most Jetski shops will have them Mikuni SBN is used on most brands.

[hyoctane23]

As promised, here are some pics of my little project. I have a SMALL problem. I noticed on one of my old pistons, there is a number 50 marked on top of the piston. I'm assuming this means it has been bored over 0.5 mm? The ski had some work done a while back and had a piston replaced. They claimed they replaced the jug as well, but obviously they did not. I might be in the market for a standard size jug. I swear, it's one thing after another. Ah anyways, pics...

1. The crank soaking in some diesel to clean stuff up...
2. My wonderfully cleaned crank case!
3. BOX 'O PARTS!!
4. The hull needs a little bit more work, but it's getting there.
5. My cramped garage.
6. Here is the piston with damage. I really think it was a foreign object because the head has some similar pitting.

[xlint89]

Hey bro, it's a tad late but you should replace them crank seals if you're this far into it. They're only $16 for the set from Denniskirk.com or Atlanticjetsports.com. Hate to see you do all this work and have an air leak because you cheated and reused a cheap and VITAL seal.