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  1. #1
    Myself's Avatar
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    Ultra 250x engine rehab, guru advice please.

    I've been wrenching on skis for over 10 years. Help out in the 2 stroke sections as much as I can. VERY familiar with them as that's what most of my customers own. This is the first time tearing into the Kawi 4-stroke although I've rebuilt several Rotax 4tecs, bike and ATV engines, as well as high performance auto engines and transmissions. I prefer to get things right the first time and I'm sure there are probably things that need done to improve reliability. That's where you guys come in.........tell me what I need to know.

    Background; Customer complains that ski is going through a lot of oil and is down on power. Around 100 hours on this. Found low compression on one cylinder.....uh-oh. Seen this before, grabbed borescope, cracked piston.

    Pulled engine
    Click image for larger version. 

Name:	250x engine pull.jpg 
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ID:	405262

    Supercharger and intercooler were FULL of oil.
    Click image for larger version. 

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    Last edited by Myself; 01-12-2017 at 09:08 PM.


  2. #2
    Myself's Avatar
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    And got it mostly torn down to remove this
    Click image for larger version. 

Name:	250x piston crack2.jpg 
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ID:	405263 I don't even know how this thing didn't come apart and blow the whole case to pieces. It obviously ran for a while after it split. Cracked straight through into the wrist pin bosses.Click image for larger version. 

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    Not sure about this rod. Looks like it took quite a bit of heat, wrist pin was stuck in it pretty good.
    Click image for larger version. 

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    What do you think?

  3. #3
    Myself's Avatar
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    Head and cylinders all look good. I'll go ahead and dis-assemble the head for some bowl cleanup and valve inspection/lapping. Also worried about these gall marks on the camshaft.Click image for larger version. 

Name:	250x cams.jpg 
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ID:	405266 Can't feel any grooves but looks like maybe the oil got very low or hot. There are also corresponding chatter marks on the valve buckets.Click image for larger version. 

Name:	250x valve buckets.jpg 
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ID:	405267 Can't feel anything with a fingernail, thinking probably hit it with the rotoloc red discs to polish them back up. Again....what do you guys think?

  4. #4
    Myself's Avatar
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    And last thing for now, also found this crack near the outer sc mounting boss. Click image for larger version. 

Name:	250x sc mount.jpg 
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ID:	405268I feel like possibly the vibration from a broken piston might have caused this.


    Discuss........

  5. #5
    nicjak's Avatar
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    The crack is common check the sc mount at the oposing end. They crack from the weight of the sc when guys flatland them jumping. Only way is to plate the mounts.

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  7. #6
    LindenPWC's Avatar
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    mostly looks like carbon build-up from cracked piston. a little wire wheel will clean it up.

  8. #7
    Myself's Avatar
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    I'm sure I can clean up the rod, I was just worried about it taking a bunch of heat and losing strength.

  9. #8
    Myself's Avatar
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    About to order parts for this thing.Should I go back with stock 260 pstons? Or back with a set of 9.5:1 forged? If I go withthe 9.5:1 does anything else need changed? Going to do a valve job and some port cleanup as well. What other upgrades/changes should be made to increase reliability?

  10. #9
    nicjak's Avatar
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    Keep it stock increases reliability. No point doing ports. They are already fine

  11. #10
    Take the time to smile sirbreaksalot's Avatar
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    Quote Originally Posted by Myself View Post
    About to order parts for this thing.Should I go back with stock 260 pstons? Or back with a set of 9.5:1 forged? If I go withthe 9.5:1 does anything else need changed? Going to do a valve job and some port cleanup as well. What other upgrades/changes should be made to increase reliability?
    I our son ally would do 9.5

    Just picks them up a bit , but obviously it's only a premium fake ski then on in

    But stock is cheaper and still a good safe option

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