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  1. #1

    Bought an Ultra 150 :) Tossed #3 Piston in 10 minutes :(

    CLIFF NOTES: Look at the pics below and give your opinion on what caused this.

    FULL VERSION:
    Been a boat guy for years. Some rearrangement of finances meant rearrangement of toys and a Jet Ski seemed the best means of water time. I picked up a "rebuilt" '99 Ultra from a 65ish year old retired mechanic. I'm a big fan of NOT buying a fresh rebuilt anything much less a two stroke. He had the right answers, ran a repair shop, said he bought the top end cyl/pistons from SBT etc and had it on the water once after he finished it. I buy it shortly after.

    I take it out for the first time this weekend. It has 50:1 Pennzoil synthetic in the gas along with the oil tank. I never got the RPM's over 5k and kept it under 3/4 throttle. Water is too cold for my taste so I didn't wanna get wet shows how easy I was riding. I just wanted to get some time on the rebuild so I could rag on it come lake season.

    I had a 5-10 minute ride out of the no wake zone then I did a few figure 8's, would run straight for 1/4 mile, do a few more lazy donuts, run straight, etc. After maybe 15 minutes total I was running about 45mph it dies. Hrm ? I sit for a second and it fires right back up. I'm thinking loose connection. I turn back towards the dock get up to about 45 and it dies again. Wont start after this so I get towed back in.

    Get home and compression is #1 = 120psi, #2 = 120psi, #3 = 20psi. I pull the dome and pistons is pitted, cylinder wall is scarred above exhaust port on one thrust side.

    So I make this first post hoping for help/opinions on what caused this. I feel like I can get the thing back together, but would love to find the culprit before toasting another cylinder. If it just needs one cylinder, do I pull the motor, or do it in the hull?

    Pics to follow.

    ---------- Post added at 10:26 PM ---------- Previous post was at 10:13 PM ----------

    More at http://gobeer.net/Ultra150/index.html

    #3 Cylinder




    #2 Cylinder



    #1 Cylinder



    Heads


  2. #2
    Sorry about your mis-fortune...

    Does it have the triple pissers installed where you can see the water flowing from each cylinder head? If not something could of clogged up one of the cooling lines and then run hot which would also make it detonate.

    Next I would check the carbs.... Make sure all the vacuum slides are operating properly and sealed and then check the jets especially on the cylinder that burned up.

    Also how long had the ski been sitting up?

  3. #3
    Quote Originally Posted by Shan View Post
    Sorry about your mis-fortune...

    Does it have the triple pissers installed where you can see the water flowing from each cylinder head? If not something could of clogged up one of the cooling lines and then run hot which would also make it detonate.

    Next I would check the carbs.... Make sure all the vacuum slides are operating properly and sealed and then check the jets especially on the cylinder that burned up.

    Also how long had the ski been sitting up?
    Single pissers. Got rebuilt earlier this year.

  4. #4
    jonny5's Avatar
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    Check your oil lines while your at it.. look for cracks

  5. #5
    Quote Originally Posted by jonny5 View Post
    Check your oil lines while your at it.. look for cracks
    All new lines - fuel and oil. I looked them over and didn't' see any leaks/seeping/etc so far. Didn't trace them visually but ran my hands down them, mainly wanted to get the heads off. I'm doing some reading, gonna call the guy that did the rebuild tomorrow. See if he replaced all three piston/cylinders. I was under the impression he did, but I can't seem to make out the 'std' marking anywhere on the third piston which has got me thinking I didn't get the whole story when I bought it.

  6. #6
    Moderator DrewNJ's Avatar
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    IMHO it looks like a large air leak. Either crank seals, missing/leaking carb base gaskets, etc etc.
    Also, the wash on the #1, #2 pistons is really odd...but that may be because of how little run time is on the motor.

    So many engine builders overlook how important it is to pressure test a motor before installing it.....

    Good Luck and welcome to the forum.
    Doug

  7. #7
    x2ryder's Avatar
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    Cold seize? How cold was the h2o?

  8. #8
    pokechop2006's Avatar
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    look at the carbs for problems,i tossed two pistons last year before i figured it was the carb diaphram, it wasnt sealing to the body because of trash an such.so im guessing mine was a high speed lean out,also could be the water temp too.

  9. #9
    I'm guessing water temps in the high 50's low 60's? Its the Arkansas river around the AR/OK border. How cold does it have to be to worry with these things? I hadn't given cold water a thought.

    I built a $20 stand tonight out of some old lumber/harbor freight casters/screws. If the casters hold up, I think the cart is strong enough. Casters might come off anyways since they dont have brakes on them and I would like it lower to work on the ski. Now this thing can sit in the garage without tripping over a two ski trailer.

    I'm still wondering if I should pull the motor, or replace the one cylinder in the ski.


  10. #10
    pokechop2006's Avatar
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    it can be done in the ski the biggest pain is pushing the rings together to slide the jug back on an you will have to loosen the whole motor so that you can rotate it to an upward position to get the jug off.

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