1994 750sx Crankseal Replacement ó how important?
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  1. #1
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    1994 750sx Crankseal Replacement ó how important?

    Iíve seen posts stating that itís recommended to replace the crankseals on older skis. How ďnecessaryĒ is this? Asking as the stock ski runs perfectly now... so donít want to get into issues by attempting something that I havenít done before (and Iím trying to keep the ski DIY).

    Iíve done the oil block-off and may pull the engine for the crankcase block-off. Seems this would be the right time to replace the crank seals.

    How hard is replacing the seals? Iíve looked around and havenít found a ďwalkthrough guideĒ... does one exist? Or is it really just splitting my the case and pulling the seals off and replacing them (with a bit of grease)? Any special tools required?

  2. #2
    PWCToday.com Is My Home Away From Home BLRider's Avatar
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    Re: 1994 750sx Crankseal Replacement ó how important?

    If you already have the engine out you're half way there. Pull off the flywheel and coupler and remove the bottom case half and replace the seals. Probably an hours work with the motor out already. ONLY USE OEM SEALS!! all other options won't last as long.
    Never argue with an idiot, they will drag you down to their level then beat you with experience.

  3. #3
    PWCToday.com Is My Home Away From Home theVetteman3's Avatar
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    Re: 1994 750sx Crankseal Replacement ó how important?

    10000000% on changing the crank seals, especially if you've already started disassembling the engine. Definitely do the crankcase blockoff too. For the exact procedure on this, including bottom half engine bolt torques and torque sequence, you can find in a 750sx maintenance manual. PDF versions are online, I'm sure you can find one if you search a bit.

    Crank seals wear out, and their material turns hard after a certain amount of time. I'm not sure how long exactly, but I personally don't trust anything more than lets say 6 years or so. Usually if I haven't replaced them, or it has been about that time, then I put the engine in my next tear down cycle to replace them when I can. Old seals leak in varying amounts. These air leaks can be hard to notice or diagnose at first, but begin to manifest themselves in the form of weird or not consistent engine performance, hard tuning when you put mods on the ski, and potentially if bad enough runaway conditions. I've had engines with bad leaks which at first manifest themselves as throttle non-linearities. As in you give a throttle input, but the actual engine reacts differently, revving a bit higher or jumping around not following what you're doing. This eventually leads to a condition where the engine will just rev out of control and get hot enough to run away and have compression ignition, where it'll keep going even if you pull the plug wires. Then you're only a few seconds away from toasting the engine.
    Last edited by theVetteman3; 03-07-2019 at 06:53 AM.
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  4. #4
    PWCToday.com Is My Home Away From Home john zigler's Avatar
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    Re: 1994 750sx Crankseal Replacement ó how important?

    Really pretty easy to do, and as stated above look for a shop manual for your ski. It will give step by step instructions with torque values.

    Quality Japanese ARS seals and case sealer in stock here;

    https://www.watcon.com/engine/crank-seals/crank-seal-1
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  5. #5
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    Re: 1994 750sx Crankseal Replacement ó how important?

    Quote Originally Posted by theVetteman3 View Post
    10000000% on changing the crank seals, especially if you've already started disassembling the engine. Definitely do the crankcase blockoff too. For the exact procedure on this, including bottom half engine bolt torques and torque sequence, you can find in a 750sx maintenance manual. PDF versions are online, I'm sure you can find one if you search a bit.
    Ok, I have a manual — will check for procedure (didn’t realize there were seal replacement instructions).

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    Re: 1994 750sx Crankseal Replacement ó how important?

    Quote Originally Posted by keck View Post
    Ok, I have a manual — will check for procedure (didn’t realize there were seal replacement instructions).
    Look in the crank installation section.
    RCJS also doing business as WATCON
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  7. #7
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    Re: 1994 750sx Crankseal Replacement ó how important?

    hardest part is going to be pulling the coupler and flywheel off. FYI the harbor freight puller https://www.harborfreight.com/bolt-t...set-62620.html worked like a charm on my 650 to pull its flywheel on the original motor i tore down. Ended up getting a motor with good compression, but am still going to do crank seals on it if i can get the damn coupler off....

  8. #8
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: 1994 750sx Crankseal Replacement ó how important?

    Coupler removal;
    Bring rear piston up just enough to close the exhaust port.
    Feed a couple feet of clothesline rope through the spark plug hole leaving a bit hanging out to pull on.
    Rotate crank ccw looking at the coupler so the piston smashes the rope against the dome.
    Spray a bit of penetrating lube between coupler and engine.
    Heat coupler up until lube starts to bubble and burn off.
    Unscrew the coupler using a big 'ol pipe wrench, should come off pretty easy now.
    Last edited by Myself; 03-07-2019 at 08:45 PM.
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  9. #9
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    Re: 1994 750sx Crankseal Replacement ó how important?

    Planning to use ThreeBond 1184 to seal the case. From what I can tell... 1184 is for liquid gaskets and resists mixed gas, etc. And 1211 is more for applying a thin coating to solid “paper” gaskets (but works as a gasket as well).

  10. #10
    PWCToday.com Is My Home Away From Home Chester's Avatar
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    Re: 1994 750sx Crankseal Replacement ó how important?

    Use 1211 on the cases.

    Chester
    Speed is very expensive. How fast do you want to spend?

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