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  1. #1
    JCan74's Avatar
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    Sucked up a rock

    Hey guys,

    I have an '02 XP and recently sucked up a rock and of course it got jammed in my impeller. I checked compression on both cyl's, 120 front and 50!! rear. Im pretty sure Ive twisted the crank. Now, without tearing the motor down, can anyone tell me if I can just replace the crank, or would I be better off with a new motor? Ive gotten mixed advice from a few shops around here.

    Thanks in advance

    -J


  2. #2
    KrunchovXPL-GTX-RX's Avatar
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    Wow, that is tough.

    The thing is, I cannot think how twisting the crank would cause a compression loss. Sure, it would put the crank out of phase, but it would still pump up, you see. At least, that is what I am thinking. I may be missing something here.

    At this point you need to know more about what has happened inside your engine. You can pull the RAVE valves off and get a look inside the cylinders (not a much of a look, but you can at least see some of what is going on as you rotate the engine by hand). I would not risk turning it over on the starter anymore until you know more.

    If you can not see enough through the RAVEs you will need to pull the head. If the crank was the only thing that messed up and the top looks good, you could get away with just doing the bottom end. It also depends on how many hours you have on that engine. If it is high, say over 200, I would seriously consider doing the top end too.

    You would hate to do all that work just have to re-do it in the next year or two.

  3. #3
    flyin' the friendly skies airbornexp's Avatar
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  4. #4
    aseymore aseymore's Avatar
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    Before you do anything as to tearing down. Check and see if the crank is twisted. I have seen a lot of rocks sucked up but never one to twist a crank. If you have a TDC gauge get the mag piston to top dead center. Mark a place on the PTO flywheel.You will have to have a pointer to go by mounted on the engine somewhere for a reference point for the marks. Now put the TDC gauge in the PTO cyl and find TDC mark the flywheel. Then measure from one mark around the PTO flywheel one way and then the other way. They should be the same. Be very acurate making marks and measuring. That should tell you if the crank is twisted.

    Aubrey

  5. #5
    JCan74's Avatar
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    Thanks for the replies to my problem guys, to fill you in a lil bit more. I bought the ski pre-owned, and he was the second owner, so I really have no clue how many hours are on it. I was also told that I could have "water washed" the rings? which could be leading to my compression loss. Im pretty clueless with mutli cylinder pwc motors, just really hoping the repair costs dont outweigh the ski's value.

  6. #6
    96XPSS's Avatar
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    Pull the head and post us up pics of the top of the pistons, and side of the cylinder if you can. And the dome of the head if there are any damage. I'm in agreement with Krunch, it's very doubtful you twisted the crank.

    The pistons are the weakest link in a two-stroke engine. Anything that happens, they will fail first.

    Did you pull the spark plugs and check their color? Was the low cylinder gray/aluminum in color?

  7. #7
    Work Harder, Millions on Wellfare Depend On Us! ultramaxracing05's Avatar
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    i also never heard of such thing. i'm glad you checked your compression, something similar happened to me but i ignored the low compression, and blew up my engine, i didnt suck a rock or anyhting thou, just swallowed water and made me check the compression after that.

  8. #8
    Pro-pulsion's Avatar
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    Quote Originally Posted by 96XPSS View Post
    Pull the head and post us up pics of the top of the pistons, and side of the cylinder if you can. And the dome of the head if there are any damage. I'm in agreement with Krunch, it's very doubtful you twisted the crank.

    The pistons are the weakest link in a two-stroke engine. Anything that happens, they will fail first.

    Did you pull the spark plugs and check their color? Was the low cylinder gray/aluminum in color?
    +1
    If you see a hole in the low compression piston, that is the result of detonation which is a result of an out of phase crank. Usually only happens from water ingestion.

  9. #9
    JCan74's Avatar
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    Quote Originally Posted by Pro-pulsion View Post
    +1
    If you see a hole in the low compression piston, that is the result of detonation which is a result of an out of phase crank. Usually only happens from water ingestion.
    Thanks for the input. If its out of phase, does it need to be replaced or realigned? Plus I noticed that my wear ring got pretty badly torn up from the rock, is a stock replacement part the best or are there others? Ive seen metal, plastic, and rubber.

  10. #10
    JCan74's Avatar
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    Quote Originally Posted by 96XPSS View Post
    Pull the head and post us up pics of the top of the pistons, and side of the cylinder if you can. And the dome of the head if there are any damage. I'm in agreement with Krunch, it's very doubtful you twisted the crank.

    The pistons are the weakest link in a two-stroke engine. Anything that happens, they will fail first.

    Did you pull the spark plugs and check their color? Was the low cylinder gray/aluminum in color?

    I did pull the plugs, the front cyl. looked a bit rich, and the rear looked barely used. I had recently replaced these, about 6 hrs on these plugs. The front had fouled on me, Im actually wondering now if I didnt have a compression problem before I sucked up the rock, and this accident gave me a reason to check the compression.
    Im kind of afraid to pull the head off, Ive no experience with these motors, (and its stored in a hay barn in the country), lol. Any sites with picture aided instructions? videos? Im a pretty smart guy but I dont want to make my problem worse by blindly diving in.

    Thanks again.

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