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  1. #1
    Click avatar for tech links/info, donation request K447's Avatar
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    Arrow 900 and 1050 motor firing sequence differences?

    I am helping a friend with the installation of a 900 domestic engine (rebuild) in a 1997 SL900. After some worried moments, it seems the CEN and PTO cylinders are now phased in reverse order compared to the old engine.

    Connected the shortest spark plug wire to the CEN cylinder, and the medium length plug wire to the PTO cylinder, and now it seems to run just fine (out of the water).

    I notice in the 1992-1998 Service Manual (beerdart edition) that pages 474 and 475 mention two different coil packs, and how to tell the coil packs apart, as the high tension leads are routed differently.

    In this case, the electrical box was not messed with, just unhooked and set aside when the engine was pulled, then re-connected after the rebuilt engine was dropped in. The coil pack did not change, and the plug wires were not disconnected from the electrical box.

    Question: Are there two different versions of the 900 crank shaft (1050 crank shaft would be the same, I think), or has the engine re-builder incorrectly assembled the crank shaft, and thereby changed the firing order by accident?

    If is simply assembled wrong, is there any downside to running the crank shaft like this?
    Balance issues?

    I am presuming that all three cylinders are still 120 degrees out of phase from each other on the rebuilt crank shaft, just the firing order has changed.

    What we did to get the spark plug wires to again reach properly, is we swapped the CDI connections to the coil pack for CEN and PTO coils - Black/Green and Black/Blue have been swapped.

    Last edited by K447; 08-17-2008 at 04:24 PM.


  2. #2
    ph2ocraft's Avatar
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    TDR was famous for re assembling the cranks incorrectly. You'd think they would follow what they had and rebuild it...they don't.
    Your rebuilder probably bought a crank from somebody that didn't pay attention to the model.
    Last edited by ph2ocraft; 08-17-2008 at 08:16 PM.

  3. #3
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by ph2ocraft View Post
    TDR was famous for re assembling the cranks incorrectly. You'd think they would follow what they had and rebuild it...they don't.

    Your rebuilder probably bought a crank from somebody that didn't pay attention to the model year.
    Model year?
    Do some versions or years of the three cylinder domestic engine have a different firing order?

    Other than creating confusion for the engine installer, is there any downside to this alternate firing order?

  4. #4
    ph2ocraft's Avatar
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    We ran our race boat like that for 2 years, no issues.

    I also edited my first post, it should have stopped at models and not model years. I was going to start talking about year differences and realized you would know them.
    Last edited by ph2ocraft; 08-17-2008 at 08:17 PM.

  5. #5
    Click avatar for tech links/info, donation request K447's Avatar
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    Just to clarify things for me;

    Do all Polaris domestic three cylinder PWC engines have the same firing order?

    What is that firing order (starting with MAG)?
    MAG-CEN-PTO, or MAG-PTO-CEN?

  6. #6
    PolarisNut's Avatar
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    I know what the service manual shows, but my 96 900 was 1-3-2 just like all of the other domestics. The coil wiring WAS changed though, which made it look like the firing order changed.

  7. #7
    Rasta Mon Condoms We Be Jammin!!!!! TxVirageTx's Avatar
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    something like this

    the 900's had one firing order,then it got changed,the 1050's using the same crank have the newer firing order.somebody rebuilds the crank for the most common firing order knowing all you have to do is switch 2 wires,either the coil wires or the trigger wires for the cdi to correct it.

  8. #8
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by TxPro1200 View Post
    the 900's had one firing order, then it got changed, the 1050's using the same crank have the newer firing order.

    somebody rebuilds the crank for the most common firing order knowing all you have to do is switch 2 wires, either the coil wires or the trigger wires for the CDI to correct it.
    Helpful info!

    Do the 1200 engines use the same firing order as the 1050, and 'newer' 900 engines?

    As fas as I know, the 900 engine was only sold for 1996 and 1997, and my friend's original '97 SL900 engine had the opposite firing order from the rebuilt 900 engine. So perhaps the rebuilder used the 'old' 1996 900 firing order for the rebuild

    1996 was also the first year for the 1050 engine. Does that mean that some 1050s also have the different firing order?

  9. #9
    1996 SL900 & SL700 turk0004's Avatar
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    so what was the conclusion on this? did the crank rebuilder actually reassemble it wrong? how did the motor react when the firing order was mixed up? was it maxing out at a certain rpm? how could you tell something was wrong?

  10. #10
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by turk0004 View Post
    so what was the conclusion on this?
    did the crank rebuilder actually reassemble it wrong?

    how did the motor react when the firing order was mixed up?

    ...how could you tell something was wrong?
    Engine ran REALLY roughly when the spark events did not match the crank shaft firing order

    Apparently both crank shaft firing orders work just fine, you just need to figure out which you have, and swap the #2 and #3 coil primaries to match the actual firing order.

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