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  1. #1

    low compression # 4

    running late and rushing I fueled the 2005 12f with 87 oct, on the way back to the dock from a 3 hour ride eng started to miss, compression on # 4 is 80, so need pistons, some where on here I think I remember reading that latter model updated pistons can be used, what's the latest year model pistons that can be used ?
    Last edited by 123456; 09-19-2013 at 09:04 AM.


  2. #2
    Banned User
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    What's wrong with 87 in a 12f I'm confused

  3. #3

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    A lot of people here are recommending it to help curb detonation issues and to be honest it's a good idea as there is a lot of heat mixed with high revs. I have always ran 87 in my '03 12F and never had any issues, however with that ski getting up there in hours and age, and the fact that now that I have the new 300 and it makes time at the gas station easier, I have switched everything to 91+...

  4. #4
    Pain is fear leaving your body.... rlovebk's Avatar
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    Check the last 2 numbers on your ecu and report back what they are.

  5. #5
    ran it all last year with 93 oct and no problems but 1 tank of 87 oct and lost atleast # 4 piston, so I chked the owners manual and it calls for 87 oct, went to chk the ecu # is 21175-3729, either way ill still need pistons, can anyone answer what's the latest year model pistons that can be used in a 2005 stx 12f ?

  6. #6
    RLACEMAN's Avatar
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    The 12f's did have this problem, not all the years (I know 05 & 06 had issues) & the problem wasn't the pistons, it was the ECU advancing the timing too far, & the motor self destructed which as you have discovered if you ran premium fuel there wasn't a problem, & with more fuel containing ethanol coming to the market during this time made the problem even worse. A good friend had purchased a new 06 model & by the spring of 07 is was getting its 3rd motor installed under warranty, Kawasaki did at that time replace the ECU to take care of this problem, he never drove again to find out if it was ok, he sold it the day he picked it up from the dealership that repaired it. So after rebuilding your motor you need to address the ECU problem so it doesn't repeat itself.

  7. #7
    21175-3729 is what I have now and shows obsolete, so ive ordered the piston and ring sets and may have to run 93 oct if cannot find a compatible ecu, is the 3732 or 3736 module compatible with the 05 12f ?

  8. #8
    RLACEMAN's Avatar
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    3736 is the replacement if you look up Kawasaki parts, 3729 & 3732 appear to be the problem ones, its an expensive part, but still far less than replacing pistons, or ALWAYS remember to use premium fuel.

  9. #9
    TexasZ's Avatar
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    Quote Originally Posted by RLACEMAN View Post
    3736 is the replacement if you look up Kawasaki parts, 3729 & 3732 appear to be the problem ones, its an expensive part, but still far less than replacing pistons, or ALWAYS remember to use premium fuel.
    Like RLACEMAN replied, the 21175-3736 CONTROL UNIT is the one you want.

  10. #10
    will there be any performance loss as felt by the seat of pants, I could run 93 oct and label the fuel fill area, as I said it ran great all last year and my bone head mistake cost me the pistons, would be great if the cyl plating is undamaged though.

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