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  1. #1
    madtom's Avatar
    Join Date
    Apr 2018

    My winter rebuild project 2003 12f STX

    looking to start the rebuild of the " my second Ski" 12f 03STX this winter. I was wondering if anyone has a done a guide or illustrated an engine rebuilds of a 12f or 15f? I know most of this stuff is almost a direct linkage to the street ninja motors. just want some pointers on engine tear down and assembly that the factory may have left out of the service manuals (which I have).

    i have noticed some trying to escape using the wonderful guaranteed to quit working at some time kawa dash meter. I used a 5 dollar polarized filter for a phone and some shipping tape to fix the dash on the 900.

    I have seen no successes other than some of smokesevin's builds using MS or standalone on some of his kawa motors. I am not that gifted so unless someone shows me a way to use the ski with only analog gauges then i am stuck with the factory dash it has to get some data from the ecu as there are some things displayed that have no wires going to the dash.

    I know the ski should be reliable once i get it back to operational boys put like 90 new hours on the 900 during the summer months(i live on the water) and all it really got was a good breakdown/cleaning/new rings/and a pump repair to bring it up to speed.... here is a pict of the 900 after it running again.

    I am trying to do this for the 12f and want the pride of doing it myself and trying to keep what i put into it under kelly BB value lol (only spent 200 for the ski so a budget of about 2200 to get it up and running.)

    history of the ski...bought 2 skis for dirt cheap as second owner had no time or desire to spend time figuring out what was wrong (paid more for the new trailer lol)

    the 12f only has 65 hours or so showing on the part of the meter that works. first owner didn't understand the meaning of preventative maintenance and ran the ski in brackish water along the Chesapeake along with sand from beachy areas (I pulled like a whole island worth of sand and calicfied salt out of the 900stx jugs on the other ski that was overheating with only 50 hours on the dash)

    I know that somewhere between the cooling and lubrication systems on the 12f there has been a breakdown. although i was able to get it to run last year and idle water was able to make it into the sump so the oil turned milky. drained it all out and put new oil back in before i covered it up.

    as for engine electrical the harness and the fuel system are functional so probably only need to put new o-rings into the injectors after cleaning them.

    compression was good so looks like i might be able to skip the pistons and rings if i want to. if i do choose to replace pistons which brands would you recommend ( nothing against SBT just trying to see what else is out there) .

    i have a spare oil cooler to see if the old one has corroded thru that is where the breakdown is I still want to upgrade to the version that mounts on the block as it seems to be fewer things that can go wrong.

    exhaust manifold and 4 into 1 are solid with corrosion so looking for freshwater used manifold on ebay and probably get a new 4 into 1.

    intake side waterpipe on block is earliest configuration and needs to be upgraded.

    will probably pull lower crankcase apart to inspect bearing wear, replace all seals and the oil pump parts.

    plan on replacing timing chain and all guides.

    the head is something im kinda concerned about but until i get it apart i wont know the level of corrosion and blockages of the cooling passages. even if everything checks out a lap job and new vallve stems seals are probably a good investment.

    I plan on using oem gaskets as they seem to have a better track record than some of the others out there.

    i plan on redoing the pump and impeller while the engine is out and all cooling lines so i should be good for a few years.

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  2. #2
    steve45's Avatar
    Join Date
    Feb 2008
    You had me wondering with that picture of the 900 engine!

  3. #3

    Join Date
    Mar 2010
    Long Island, NY
    If the motor runs and has good compression, why tear it down? It's possible that the cause of water in the oil is not due to anything inside the engine. Water can get into the oil in a variety of ways, including water in the fuel tank, water in the intake manifold and corrosion in the exhaust manifold. If you can solve that problem without an engine re-build, then you'd be better off just fixing the problem and using the ski until you actually need to re-build.

    Even if you decide to go for the re-build, you should first figure out exactly where the water is coming from. If you don't you may end up dumping water into your newly re-built motor.

    For my first 15f re-build, the best tool was the digital camera. I took many photos at each step of the tear-down. Re-assembly was easy using the pics as a reference. I've built two more since then using the same pics as needed.

  4. #4

    Join Date
    Mar 2010
    Long Island, NY
    What was the point of that filter on the dash? If the plastic is scratched and cloudy, there's a better solution. You can get one of those headlight cleaning kits. I cleaned up a Yamaha dash by wet-sanding with 600 grit sandpaper and then using polishing compound to buff it out. Looked almost as good as new.

  5. #5
    Pain is fear leaving your body.... rlovebk's Avatar
    Join Date
    Aug 2008
    So. Cal.
    Chances are the exhaust manifold is probably where your water is entering your motor. There is a nipple down low that degrades and does this at the collector.
    Cool project. I have many parts for 12F motors but unfortunately no exhaust parts. They tend to be pricey as there are not many but that is just supply/demand on the used market.
    Good luck and PM me if you need anything.

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