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  1. #1

    Join Date
    Jul 2011
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    richmond, va
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    xlt 1200 help. Premix ski loses rear cylinder, possible causes?

    Hi all, looking for some thoughts from those in the know. Have two xl1200s. Took them out for the first time this year. Within short time frame of handing off to my son, he returned stating ski was stalling. I took it for a ride, ran and idled smooth but no top end speed (32mph max), bogging badly on take off. Was wondering originally if the powervalves were sticking or possibly bad plugs. Put new plugs in ran the same. Tried to get it back to the dock and it did the slow death stop cylinder freeze . Was unstuck by the time I towed it to the dock. Lost compression in the rear cylinder (30psi). Front two balanced around 115-120ish. Ski is premix so that this would not happen, only use amsoil and 40:1 if I recall and I only use non-ethanol fuel. My thoughts on possible root causes:

    1. remotely possible i could have missed the oil after the last fill up but unlikely as I fill them both at the same time, no issues with the other
    2. crank shaft seal leaking in the rear
    3. carb issue (was reported to be rebuild by PO shortly before we got it, so within 5 years most likely, so I would not think thats the issue.
    I am assuming is that running too lean is the only real cause, but am I missing something? Where would you start?

    I did do a quick prime start on it before i took it out and noticed it seemed harder to start than usual. Anything else that I am missing as a possible cause? Can head gaskets go on these? Any tests I should run before tear down? Dont want to fix it without nailing the true fault, been there done that....I want to do it once only. Getting to the point I am feeling too old for the effort on these, although I love my yamis.....

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  3. #2
    steve45's Avatar
    Join Date
    Feb 2008
    Location
    Texas
    Posts
    7,649
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    Well, now you've learned that pre-mix isn't all it's cracked up to be.

    With the Yamaha oil injection system, the cylinder still gets oil even if the carb gets plugged up and it doesn't get fuel.

    The carbs might have been overhauled 5 years ago and you think that's OK after you burned up the engine? Really?

    Do the whole engine. Go through the carbs, replace the crankshaft seals, pressure test the crankcase. Use genuine Mikuni carb parts--ONLY.


  4. #3

    Join Date
    Aug 2016
    Location
    Panama city
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    327
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    23
    Stock jetting?.stock ski??.still have the cat?..Most don't, see use the European jetting on page 26 of the recipe (they did not have factory Cat)..92.5 pilot and do the fuel pump balance mod in the same F&Q seatio.

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