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  1. #1

    Oil lines good,pressure tested,reeds look good still toasted the rear piston ??? Help

    I have 2 00 XL limited 1200 skis and they both lost the rear cyl. I pulled the pipes and checked everything oil lines still attached with oil in them at the carbs carbs have lots of traces of oil inside, reeds looks good on one ski the other with carbon reeds they have a few broken corners but look to still be sealing. I pressure tested both engines and they leak from 10psi down to 6psi and then hold there for hours. Carbs are a question as I bought the skis used and I do not know if they have ever been rebuilt. Both skis still had the cats in and one is completely broken apart and sitting down the pipe a ways from where it is supposed to be the other is still in place but is broken up a few pieces floating around. The pistons almost look like they may have spun a ring but I highly doubt that is possible. The power valves are still intact and do not look to have dropped no wave eater clips but they still have the pins in place and no play that I can see that would cause them to contact the piston.

    My questions for the guru's on here is ... Could the cats cause a rear piston failure or do I have other problems ?

    I hope to have a few pics of the pistons tomorrow or let me know what other info you guys need to help me figure out what happened.

    I greatly appreciate any and all help

    Thanks
    Last edited by chevydog; 07-07-2013 at 08:58 PM. Reason: More info added


  2. #2
    Banned User
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    See these same words constantly on here.... " carbs are original as I just bought ski".... Trying o save 200-400 just cost you that x2 or 3 times. First thing anyone with a used 2 smoke should do is go thru carbs, premix, new plugs, new fuel n oil, new fuel filter, new fuel lines.

  3. #3
    Thanks for those words of wisdom a little late now but I would still like to know if the cat could have caused the rear piston to fail or is that totally off the table and I need to look elsewhere.

    Carbs going to be rebuilt regardless.

    Thanks

  4. #4
    TexasZ's Avatar
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    .............
    Last edited by TexasZ; 07-09-2013 at 11:19 PM.

  5. #5
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    For me, leaking from 10 PSI to 6 PSI means you have an air leak. Although I am sure your problems were caused by carbs.

  6. #6
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    The cat can defenitaley cause a rear piston size. It can break apart and lodge down in the pipe and it will seize the rear cylinder only.

  7. #7
    TexasZ's Avatar
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    My apologies, I should have read your post again and paid closer attention to the details.

    At least my post brought on the way more knowledgeable people...and I got to learn something too.

  8. #8
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    It also should hold the 10 psi for a long time. A slow leak like that I find at the rear crank seal sometimes. Is it enough to cause a problem ? maybe but should be fixed. Another place is where u are sealing things up. Sometimes a leak is there.

  9. #9
    Thanks Rocketman, the leak from 10psi to 6psi is deffinetly at the rear seal when I spary it the bubbles are there until the 6psi and then all is good. I have two of these skis and they both have the same result with the pressure test. Anyway to be safe I think I will pull the engine and put in new seals and see what happens, I am almost that far into it anyway.

    Thanks again.

  10. #10
    Yamaha artisan Cutlass's Avatar
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    During engine operation, the crankcase (pulse) is probably only plus or minus 4 psi. Maybe 5 psi. Maybe 3. If your crankcase holds 6 psi without leaking, its probably ok.

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