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  1. #1
    Legend in my own mind Sirhc7897's Avatar
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    "Wobble" in the motor

    Question on engine installation...

    My motor is very well aligned per bolting up the alignment tool (slides in and out of the driveshaft coupler freely) but when I install the pump and driveshaft and turn it over by hand I can see the motor trying to flex on the motor mounts...It is happening exactly 180 degrees apart...

    Anybody experienced this? Would the front of the motor being too high cause this (even though is seems as if that was the case the alignment tool would not have slid in properly)?

    Pump out of round, driveshaft warped (though it is brand new and never run)...

    Just looking to get ideas for troubleshooting from those with experience with aligning the doo 2 strokes...

    Also, just how absolutely critical is alignment in these...How much tolerance is there?

    Thanks...


  2. #2
    steach's Avatar
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    Are your motor mounts sound? Push and pull on the pipe to ensure there is no lift.

    What you may be feeling is the crank cycling a piston to/from TDC. By turning the crank by hand you are pulling the piston down as opposed to combustion pushing it down. This can cause a "wobbly" feel.

    -if the tool fits...wear it.

  3. #3
    on mine it was a bent shaft

  4. #4
    96XPSS's Avatar
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    If the spark plugs are in it then that is normal resistance to compression. 951's shake pretty good at idle if you never noticed, so flexing on a compression stroke is probably normal.

    Pull the spark plugs out and see if it is smooth all 360 degrees.

  5. #5
    Legend in my own mind Sirhc7897's Avatar
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    OK so I guess I'll elaborate a little more...

    It is a carbon fiber GSX with a Polaris 1200 superstock motor going in it. The pump is the sea doo pump, the driveshaft is a Sea Doo HX driveshaft and the coupler is a hybrid put together to extremely tight tolerances by a machine shop (they pressed a doo coupler into a Polaris coupler for me so it would work)...

    It is bolted down using 4 standard sea doo front motor mounts through custom corss bars attached to the engine. There are no plugs in the engine at the moment...

    And the Polaris 1200 shakes just as bad as the 951...Motor is very secure...

    So now that we've all realized that I omitted way too much info (I apologize but thought since it was a true doo driveline...) we still think these things apply...

    I'm just trying to figure out if I should be worried about it or not...The thing will be spinning about 8k and making 230-240hp when all is said and done so I'd imagine it'd chew something up pretty quick if it ain't right...

  6. #6
    96XPSS's Avatar
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    Ok Chris...that helps alot!

    Have you rolled the HX driveshaft on a flat surface (like a pool table) and verified it's trueness?

    SD alginment tools can fool you, they can be bent too. If your shaft is true, make note of where the bind point is, and what the engine is trying to do when in that bind. Is it trying to lift? Swing sideways?

    I always algin by bind point inside the PTO, instead of relying on a tool. Slip the driveshaft into the engine PTO, leaving off the pump. Swinging it side to side, finding the point when each side binds, then position the engine so each bind point is equal from the center. The center is the middle of the pump (rideshoe) opening. Same way vertically. Then shim the engine accordingly.

    Either your alignment tool is bent or your driveshaft...from what you describe.

    Keep us posted what speeds you run when you get her dialed...

  7. #7
    Legend in my own mind Sirhc7897's Avatar
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    Cool...Every little trick I can have up my sleeve to test it and make sure it's right thrills me...

    I am in the process of getting everything installed and mounted at the moment...Should have it all put together in the next month or so and start dialing it in...

    No clue yet exactly what to expect but the thing previously ran about 61 on a stock motor with buckshot 48's with wicked holeshot and about 67 with twins on stock motor...

    It should be a monster if it holds together...

    I certainly appreciate the help...

  8. #8
    Legend in my own mind Sirhc7897's Avatar
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    BTW - got a thread running on it here for anyone interested...

    http://greenhulk.net/forums/showthread.php?t=21227

    It's been going painfully slow but now with my wedding out of the way and my schedule settling down it's getting back on track (plus it's a little cooler in the workshop which is a motivator too...those 98 degree days just do not make you want to go work in the garage...)

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