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  1. #1
    I'd rather be riding!
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    Ultra 150 Rebuild

    I'm new to the forum and need some help -- Bought a 00 Ultra 150 last year. Rode for about one month, then lost compression in the rear cylinder. When I started working on the engine, I found the carbs were loose--think this may have been part of my problem. Finally got around to rebuilding the engine a few weeks back.

    When I removed the head from the rear cylinder, it looked like someone attacked it with an ice pick -- Pre-ignition/detonation I think. Installed replated cylinder and new piston and rings.

    Added oil to my gas for the break in period. Road last week--nice and slow to break in the new items. Ski ran good. Went back out yesterday and the ski was running great--then I lost power. Haven't checked it yet, but think I lost the #3 piston again.

    Any tips on what I may have missed so I don't repeat this again?

    Also recently rebuilt my 96 ZXi. Must be a slow learner, because I had to replace the piston on it 2 times as well.

    Help.

    Will be replacing the rear cylinder on my 04 XLT next week. Oil line popped off, so I'm removing the oil pump and mixing my gas from now on.

    Thanks in advance for any help.


  2. #2
    steve45's Avatar
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    Welcome aboard, jkv1216!

    Sounds like this just isn't your summer...

    The damage to your cylinder head is probably from pieces flying around the cylinder. Could be a spark plug electrode, pieces of piston, and/or piston ring. Detonation will usually put a hole in the top of the piston.

    Did you install an OEM piston & rings? Look for a plugged water passage at the elbow in the cylinder head. Also, make sure the oil lines are hooked up to the carbs AND the balance shaft bearings. Don't try to go pre-mix on the Ultra. What pre-mix ratio were you running for break-in?

    I think you'd be real smart to go through the carbs. The Ultra will not tolerate running lean, and the result is often catastrophic.

  3. #3
    I'd rather be riding!
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    Thanks for replying Steve.
    I mixed the tank at 50/1 for the break in. I think the problem is too lean a mixture, but not sure what the cause is. Oil pump seems to be working well. Heads/cylinders are staying cool. I stopped every 15 min or so and could touch the cylinders and they were cool to the touch--vs the ZXI which gets almost too hot to touch.

    I've posted some pics of FB that may give you a better idea of the problem -- https://www.facebook.com/media/set/?...5217978&type=3

  4. #4
    I'd rather be riding!
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    Thanks for the reply.

    I mixed the gas at 50/1 for the break-in. I do think the problem is from running too lean, but not sure what the cause is. Initially thought the original failure was due to the carbs not being tight, but not sure now.

    I think the water flow is good. Stopped every 10-15 min to check the cylinders and they were cool to the touch--vs the Zxi that is almost too hot to keep your hand on.

    I'll definitely go through the carbs when I pull the engine back out. Got to put the XLT back together first. Going to an oil block off on the XLT so I don't kill it with another oil line coming loose.

    Posted some pics on FB that might give you a better idea of what happened -- https://www.facebook.com/media/set/?...5217978&type=3

  5. #5
    I'd rather be riding!
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    Must be doing something wrong with my reply--doesn't seem to show up. 3rd try.
    Thanks for the reply. Guess this is my summer to hone my Jet Ski rebuild skills.

    I've posted some pictures on FB that may give you a better idea of the original damage -- https://www.facebook.com/media/set/?...5217978&type=3

    I replaced the cylinder with one from US Chrome. Piston and rings were from WSM.

    Researched the damage and seems like pre-ignition to me, but I'm new to this.

    I used 50/1 premix--along with the oil pump--for the break in period. But still think the ski was running lean on the rear cylinder. Any idea's why?

    Pretty sure the water is working. Stopped every 10-15 min to check the cylinder temps and they were cool to the touch--vs the ZXi which runs almost too hot to touch.

    I will definitely go through the carbs when I pull the engine again. 1st I've got to get the XLT back together. I'm definitely going to go to the oil blockoff on the XLT so I never lose another cylinder due to a loose oil line.

  6. #6
    pics ?

    dont do facebook.

  7. #7
    steve45's Avatar
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    50:1 + the oil injection should be good for break-in.

    I don't do Facebook, either. Easy to post pics here.

  8. #8
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    Could be carbs, air leak from a bad crank seal, a twisted crank, maybe the motor had been hydrolocked in the past????? I would suggest checking all of that.

  9. #9
    I'd rather be riding!
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    Click image for larger version. 

Name:	Damaged Head and Piston.jpg 
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ID:	274604 Damaged head and Piston.
    Click image for larger version. 

Name:	Ultra Engine.jpg 
Views:	167 
Size:	129.7 KB 
ID:	274606 Engine.
    Next time I'll have to take more pics of the disassembled engine. I've never hydrolocked the engine, but I've only had it a short time, so may have happened with previous owner. Someone definitely worked on the engine before I purchased the ski. Had to replace two helicoils in #2 before I could put it back together. Click image for larger version. 

Name:	Helicoils.jpg 
Views:	113 
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ID:	274610

    Change of subject--removing power valve from my XLT tonight. I've read a lot about the pin falling out, but I can't get the pin out of mine. Any suggestions?
    Keith

  10. #10
    I'd rather be riding!
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    Click image for larger version. 

Name:	Cylinder and Piston.jpg 
Views:	191 
Size:	134.5 KB 
ID:	274611Picture of the piston in the cylinder before I pulled it.

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