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  1. #1

    Join Date
    May 2015

    superjet piston only moves halfway.

    Hey guys, i new to forums so forgive me if i do something wrong. i recently bought a 1992 yamaha superjet and its been giving me some troubles. I just put a new battery in it and when i hit the start button i heard the starter engage but the motor didnt turn over . so i decided to pull the plugs to see if it would turn over and it didnt. This ski has been sitting for about 10 years so i assumed something would go wrong. i started trying to turn the engine over by hand and it worked for about a full turn however only one of the pistons moved. i hit the start button again and they both cranked once really quickly but now one seems to be stuck at the bottom of the cylinder, it will go up halfway nut then gets stuck again. how can i get it unstuck? any help is appreciated.

  2. #2
    800AMSOIL4U's Avatar
    Join Date
    Aug 2006
    Morgan Hill, CA
    Sounds like a broken rod.

  3. #3
    Banned User
    Join Date
    Sep 2014
    Blown engine (broken rod or crankshaft).

    Hope you didn't pay much that's about a $1000 repair.

  4. #4
    Prism's Avatar
    Join Date
    May 2007
    "New" Jersey
    If the pistons only move halfway like the title says, I would make sure the impeller isn't binding on the pump wear ring. If it's free, then I would agree with what has already been said....broken rod or crank. Pull the pump back and try it.
    Last edited by Prism; 05-23-2015 at 08:12 AM.

  5. #5
    As has been stated. If one piston moves when the engine is cranked and the other piston does not, then definitely broken/damaged internal components.

    Which piston is not moving? Is it the rear?

    Fortunately, that's an easy motor to work on.

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