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  1. #1

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    Ultra 150 piston damage again!!

    I need some help in determining what is causing this engine to eat pto pistons. The first piston went along with the crank due to what I determined was rust on crank pins due to extreme long parking with no use and probably not properly fogged. The ski had a total 22 hours when I first got it about a year ago now. PTO Piston and crank went in the first hour. Piston and sleeve had scouring mainly due to metal from crank rod bearing. Rebuilt crank and sleeved rear cylinder, installed 1 new piston, 3 sets of rings. 1.5 hours later had damaged piston very similar to now. I then thought it was due to carb issue, not sure anymore. Carbs are running almost perfect now. Honed cylinder to 25 over. New piston and rings and about 5 hours on it and piston damaged again. See pics. Only thing I can think of is the sleeve I put in is not dissipating heat efficiently. The crancase and cylinder show good signs of oil, so can hardly think oil was an issue.Head on the left is PTO other is center cyl. Sparkplugs are front to rear from the left. Also attached a pic of center cyl. looks very black to me - rich??

    I need to get this thing running reliable. I am now thinking of getting new cylinder from kawasaki.
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  2. #2

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    Quick thoughts:
    Common thread is the cylinder and carbs.
    Pics are not very good!
    My first thought would be a lack of water circulation around the cylinders. Those look like hot semi-seizures.
    You are one persistent son-of-a-gun!

  3. #3
    steve45's Avatar
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    Don't forget that the front & rear cylinders on the Ultra get oil from the counterbalance shaft bearings, too. If oil isn't feeding in there right, it may have caused the crank problem, as well as the hot cylinder.

    I seem to remember reading somewhere that someone found an oil port that wasn't drilled properly, causing starvation, but I don't remember all the details.

    You might post your question on the Ultra board: http://ultra150.yuku.com/

  4. #4

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    I did check the oil passages in the crankcase when i put in the crank. They are ok. Also I am running 50:1 premix on top of the oil injection. So I should be ok even if the oil injection didnt work at all. When I pulled the cylinder I could see good traces of oil in the crankcase, so I dont think oil was the problem. I would like to know if anyone has successfully resleeved a ultra cylinder with wsm sleeve?

  5. #5
    captainoverspray's Avatar
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    my pistons looked like that and i am thinking water injestion was the cause. You running the stock arrestor or A/M? If A/M you might want to get some outerwears for them.

  6. #6

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    I run stock F/As. What other signs of water ingestion can I look for? I did not see a trace of water anywhere inside when I pulled it apart.

  7. #7

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    Not seeing anything that looks like water ingestion.......

    That piston looks like it was running with the metal temp too high...look at the piston scuffing....either too little oil, too little cooling water, too lean....either lean on gas or a shortage of oil.

    Maybe rebuild it and run it again to see?

    I noticed that no improved pics were posted, no comment/response on whether or not the cooling system was CONFIRMED to be working.

    So, good luck with that!!

  8. #8

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    Cooling system is working properly. All hoses have been checked. Other cylinders do not show any signs of heat damage. I relooked at the carbs and have a suspicion that maybe the rear carb diaphram has a small hole. Could this cause a lean condition? I will try to get a hold of a better camera and repost pictures.

  9. #9
    SPEEDFREEK SPEEDFREEK's Avatar
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    I just finished doing top end rebuilds on two of my Ultras. They both blew pistons within a week of each other. I at first thought water ingestion. I actually sent my damaged pistons to my uncle at XOM. He had someone look and determined that my damaged was caused by bad fuel.
    Have you siphoned your existing fuel out and replace with new premium fuel to run?
    I don't know if yours is the same problem, but you never know.
    We had purchased fuel at the same location for 9 years on the lake, they sold and new owners doing something different.
    Just my .02 cents.

  10. #10
    jonny5's Avatar
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    Another thing to think about is that if you add oil to your tank with the oil injection you actually start to lean your fuel mixture. People dont seem to under stand this. It's like if you run 87 then run leaded fuel ....It takes a little more to flow leaded fuel. Just like your fuel when you add more oil it takes and little more to flow thru the carb so in turn your leaning your mixture.

    Just run the thing with the oil injection only .....all this safe stuff people try to do and end up causeing problems.

    They will run 300 hours bone stock with proper maintance and inspection.

    Looks like its running hot to me. The other piston ass well..all black.

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