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  1. #1

    sl750 Semi Seized. This is a new one to me

    So, I have a 93 sl 750, last summer I was idling it out and it made a clunk and would no longer turn over. Pulled the plugs, still would not turn over manually or by starter.. or so I thought. I assumed I burned up a piston. So I pulled the heads off tonight all the cylinders look fine, and the starter engages and spins the motor about 1/16 of a cycle every time I push the button. Still cannot turn the motor by hand, or by beating on it with a rubber mallet. I was able to inspect the cylinders fully, and they look ok.

    I am not familiar with crankshaft problem diagnosis, or the symptoms of problems with the crankshaft/ bearings.


    My thoughts...

    - cylinders are in good shape so the top end is not the problem
    - crank must be at least intact because it will turn over a full cycle
    - So either the impeller is seized up- i checked there is nothing lodged in there but possibly the bearings went bad???? any thoughts on this?
    - or the a bad bearing in the crank????
    - starter should not be the problem since i cannot turn the motor by hand and it sounds like it is engaging and disengaging properly.

    Any input on the source of this problem would be appreciated, I hope this is not a repost I searched for quite a while.


    Thanks
    Dan


  2. #2
    seaobin's Avatar
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    pull the pump

    try to spin

    if a piston is stuck the starter will try to turn it and is stronger than you

  3. #3
    pulled the pump, that was not the problem. I think that leads me to a problem with the crankshaft/bearings?

  4. #4
    pistons do move, just a little at a time

  5. #5
    Click avatar for tech links/info, donation request K447's Avatar
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    I would guess that the Bendix may be seized/jammed into the flywheel.

    Of the crank bearings are really rusted tight...

  6. #6
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Pump removed and pistons out, it still doesn't want to spin?

    Check the bendix next.

    If that's good, then you have crank/piston issues.

  7. #7
    Pistons are still in, but the heads are off, and the pistons look like they can move freely ive inspected all of the cylinder walls they are ok

    so if the bendix was seized into the fly wheel would the starter still be able to turn the engine one bump at a time? like it currently does

    Is it possible to check the bendix without removing the motor? Maybe pull the gas tank? if i remember right the starter is underneath the exhaust manifold correct?

    Another thought, the day it broke it was in use for quite some time and running when it stopped, how would the rusty bearings or the bendix gear be the cause of this?

  8. #8
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Drake103 View Post
    ...would the rusty bearings or the Bendix gear be the cause of this?
    Rusty parts can seize up and fail at any time

  9. #9
    Thinking about that again, that does seem logical. I will pull of the exhaust manifold and take a look at the starter and report back.

    Thanks for all the help


    Dan

  10. #10
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Drake103 View Post
    ... I will pull of the exhaust manifold and take a look at the starter and report back...
    Bendix is accessed from the front of the engine (flywheel housing), starter motor from the side.

    Either one could be seized, or both...

    Certainly I would inspect both.

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