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  1. #1

    Shredded A Piston And Cylinder

    Advice as what to do now. Riding the machine today. Everything was fine, then the machine quit. I thought it was odd, so I swam it back to shore through BIG surf (3-4ft swells....was crazy). Anyhow, pulled the plugs, and performed a makeshift compression test (thumb over each spark plug hole). 2 cylinders had compression, 1 had nothing. Pulled the cylinder heads off and heres what I found. 2 cylinders are in great shape...smooth cylinder walls, pistons had tight seal, etc. The third looked like crushed or shaved ice (sorry, best description I could think of). The cylinder walls were etched and scored. Now, do I tear down, check everything and rebuild? Or do I sell the ski as is and get something a bit newer and less problematic? Would finding a used cylinder and buying a brand new piston and rings be the way to go? I got into the ski relatively cheap, and I don't want to spend a ton on it. Any advice here would be awesome since I'm on the verge of a breakdown (literally and figuratively).

  2. #2
    bowsniper's Avatar
    Join Date
    Aug 2008
    what kind of ski are we talking about?

  3. #3
    Click avatar for tech links/info K447's Avatar
    Join Date
    Jul 2007
    near Toronto, Canada
    If there is damage from metal debris, then there is a strong possibility a bearing in the crank case has come apart and the bits have gone up through the combustion chamber.

    Since you have the cylinder off, check the connecting rod and crank bearings for any signs of damage. There should be zero vertical slop or side-side wobble in the connecting rod, and almost no side-side clearance in the lower rod bearing.

    If the bearing has failed, then the crank shaft would need rebuilding. That takes you close to doing a full engine rebuild.

    Don't look at what you spent so far to buy/repair the machine. That money is gone.

    Look at what it would cost you to purchase another good running machine, compared to what it will cost you to get this machine back on the water.

    And remember, if you rebuild this engine you will have an essentially NEW engine. Properly maintained, it should last a long time.

    Since you will be doing the maintenance, you will be in control of how long it lasts. To the extent any of us have any control over that

    If you buy something else used, it comes with no warranty. That engine (and everything else in the ski) might last a long time, or not.

  4. #4
    Quote Originally Posted by bowsniper View Post
    what kind of ski are we talking about?
    It's a '96 SLX 780. I had advice that if any metal flakes or pieces dropped into the block or crank areas, it could have done significant damage. If that's the case, I'll have to strip the entire engine down to the last bolt and completely engine degrease the thing to ensure no
    contaminants are left. In any case with my limited time (and knowledge), this repair has most likely land locked me for forseeable future. Why couldn't this have happened on the last ride of the season??

  5. #5
    TopCop931's Avatar
    Join Date
    Apr 2010
    Nutley, NJ
    Well.....You either just found your project ski for the winter or you're going to get some of your money back in the classifieds here. If you're going to pull the motor and take down the bottom of the case to check the crank out you are going to have to replace every seal and gasket on the way back if the crank is in good shape. That's bucks. If the crank is bad that is bigger bucks. However, if you do any of that you will have a new motor or at least a sound motor as Keith pointed out.

    I am the wrong guy to be giving advice in this area because I am already in for more than my ski is worth and I didn't even get into anything related to the jugs or pistons thus far.

    In the end you have to be willing to live with the costs of either scenario of a repair. I don't put much emphasis on the time that I put into it because I am retired and need something to do anyway. Your time may be more valuable than mine so you have to think of that as well.

    It sucks dude. I feel for ya.

  6. #6
    Click avatar for tech links/info K447's Avatar
    Join Date
    Jul 2007
    near Toronto, Canada
    Every PWC owner should know that each time we press the Start button, there is a possibility that will be the last time it runs.

    Whether we take good care of the machine, or not, there is always the possibility of something going wrong. We do what we can to minimize the chances of failure, and that is all anyone can do.

    Do the maintenance and repairs, do the pre and post ride checks, cleaning and care.

    Budget (or at least psychologically prepare yourself) for potential repairs and unexpected costs.

    After that, enjoy the ride and don't worry excessively.

    If something happens, make the best choices you can. That is all any of us can do.

  7. #7
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
    Join Date
    Oct 2006
    Cleveland OH
    Well, how lucky do you feel????

    I've seen some guys replace the piston and cyl and run it as is, but, me personally....

    I'd have the engine out and disassembled already.

    Getting all the debris out of the crank bearings is a must. Spray degreaser and a little compressed air. (just don't spin the bearings at 6k RPM with the air)

    A tube of Threebond 1211 silicone ($20), a oversized piston kit ($75) and cyl bore ($60)for the 1 bad cyl (or a good used STD size cyl with piston $100) and head ($30), plus a gasket set with crank seals. ($75)

    $260 and your back together and running (best case scenario)

    But, if the damage took anything else out like the crank or top engine case half, price just went up considerably.

    How about a pic of the damage?

  8. #8
    Starting to feel pretty good about this mishap actually. The plan is to disassemble the engine down to the crank, clean, inspect and rebuild. This way I'll get to know the machine inside and out, and HOW things work. I have zero experience with anything mechanical, but I will learn it quick. Keith was right..whatever money I have spent to purchase the ski and do some minor repairs is gone. This is going to be a major repair, and a hell of a learning experience for me. I spun the crank (drive shaft) by hand and all 3 cylinders move freely and without any odd grinding, resistance, etc, so it appears from the surface the crank is still intact. Obviously I'll have a better idea once I get stuff cracked open. Luckily I work for the City, and the mechanics in our yard have been pretty helpful when it comes to my complete ignorance of all things mechanical. I think the best course of action is to get it rebuilt since I won't get too much for it not running if I try to sell as is. Secondly like I said, I want to get to know what makes these machines tick....what better way to get to know them than to have something like this happen? I imagine that the SL, SLT, and SLX all use the same piston and cylinder? If so, the parts should be fairly plentiful and easy to find. I'll get some pics up of the entire ski. Over the next little while, I am going to completely transform this ski into a thing of beauty. I was pretty ticked yesterday when it happened, but a coffee and a few deep breaths led me to think this could be a pretty good opportunity to learn.

  9. #9
    Here's some pics of the damage:
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  10. #10
    Sorry, with work, wife working afternoons and having my daughter from 3 o'clock on every day, I've only had time to crack to heads off and have a quick look. The third head has been off as well, and looks in the same shape as #2. The only damage done was to #1. Thinking I may remove the oil injection system altogether and run premix.

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