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  1. #1

    Cool 97 GP1200V Rebuild Needed? Not sure of the cause?

    Looking for some help with a rebuild on a 97 Yamaha GP1200.Have read some of the threads regarding rebuilds and they have been very helpful.My concern with mine is that Iím not sure of the cause of the #3 cylinder failing.
    My daughter was driving it recently and it suddenly quit.Wasnít running rough at all and have not had any previous problems, she was right by the dock so she floated it over and I jumped on and got it started right away and it ran great.3 or 4 days later I was ripping across the lake at just about full throttle and after 4 or 5 minutes it just quit.Thought maybe I had ran out of gas so I switched to the reserve and it started again right away.Drove back to the dock to put some gas in to discover the tank was still over half full.Pulled it out of the water and did a compression test on all 3 cylinders.Started with #1-115, #2-114, #3-50.Took one more compression test on #3 and got 0 that time.
    Took the head off to take a look to discover the #3 cylinder looked lean compared with the others and that there was chips off the edge of the #3 cylinder.There are a few chip marks in the head from the pieces that obviously came off.Everything still turns fine, can push on any cylinder and the other will move in a full rotation.When I took off the head I check all the oil lines and they were all connected and #3 line still had oil in it.Have not done any further diagnostics at this point.Not sure what the problem is and will definitely have to figure that out before I do the rebuild.Anyone have any ideaís what it might be? I will be checking the operation of the oil pump and plan on doing a rebuild with kits on all the Mikuni B44 carbs.Wondering if the carb could be the problem.(Maybe a plugged fuel filter??)or the oil pump.Have had the ski approx 5 years and have never had the carbs rebuild but have winterized and fogged with a carb cleaner every year. Not sure what else I can do to figure out what caused the lean condition.The jet ski has 200 hours on it and from what I have read that is approx when a rebuild can be expected.
    Also want to carefully fix the marks in the head of the #3 cylinder, what is the best way to do these?
    Have not gone to premix gas, feel like the system has worked well so far.At this point maybe the premix would have saved me unless itís metal fatigue (the 200 hour mark).

    Also wondering what the small piece is between the outside of cylinder walls of #1 - #2 and between #2-#3, looks like some sort of balance weight. (2nd photo) Have one that is broken and want to know if I need to replace it, can't find any info about this.

    Am considering sending the cylinderís to that from another thread that suggested using them.

    Any help or info would be great....

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  2. #2
    Join Date
    Apr 2006
    Orange, TX
    The carbs need to be rebuilt, regardless. Looks to me like the ring broke. The pieces between the cylinders are sacrificial anodes that help keep corrosion in the water jackets away.

  3. #3
    Echo's Avatar
    Join Date
    Aug 2013
    Tarpon Springs FL
    Need to do a leak down test before you disassemble any farther. That is required to properly diagnosis the problem. Search the forums, there are a couple write ups on diy leak down tests.

    That head looks pretty good I see a couple high spots that need to be ground down so you dont get detonation. It is aluminum, dremel tool with a fine/smooth stone works well.

  4. #4
    Had a local guy tell me he thinks that the rear seal went on the crank therefore causing the lean condition. Really can't decide what to do at this point. Have also had it's suggested that I drop a new engine in it for $1200 and get a 2 year warranty. Everything else with the ski is great at this point. I will definately have to do a rebuild on the carbs, this looks like it would not be to difficult for a first timer.

    Leaning towards the new engine but really don't like the $1200 that it costs plus $150 for the carb rebuild kits....

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