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  1. #1

    12f low compression - no oil burn - 6400 max rpm

    06 12f - Ski is reaching a max of around 6400 rpm..
    Installed new plugs.
    Checked valve clearance... all intakes are toward the high range and exhausts are near the low range of IN 0.15 ∼ 0.24 mm (0.0059 ∼ 0.0094 in.) EX 0.22 ∼ 0.31 mm (0.0087 ∼ 0.0122 in.)
    Pulled the pump and checked the bearings - seemed smooth and in good shape, although the wall of the pump looks like it had been gone through with a really rough hone, but no gouges
    Checked the resistance on the exhaust temp - in spec.
    Checked oil level - at or just below the dot for the cold - when cold.
    Need to Check compression again..
    Been running 93 octane -
    At low idle, like when motoring out of the channel, it will occasionally surge up one bar on the tach. Like it suddenly makes more power for about 1 sec.

    What to check next... ?
    Last edited by furn1593; 08-11-2012 at 10:40 AM.

  2. #2

    Join Date
    Aug 2009
    San Diego, CA
    I just ran into this same problem. Check you fuel pressure. The in tank fuel pressure regulators start to corrode and dont do what they are supposed to do. I purchased a fuel pressure tester and I was only getting about 30psi of pressure and 6200 rpms. It also was bogging in the midrange. I hooked up my fuel pressure tester and kinked the return line while it was running and got the pressure back up to 43 psi and it ran perfect. So now im replacing it with this

  3. #3
    ok - will check

  4. #4
    It's either piston/rings/cylinder or valve adjustments.. get 46psi fuel pressure at idle. Engine warm throttle open #1 110 psi #2 100 psi #3 100 psi. #4 110 psi. Just a note 2 and 3 pistons are sbt replacements.

  5. #5
    Anybody else have speculation as to cause of low compression and no oil burn.

  6. #6

    12f low compression - no oil burn - 6400 max rpm

    Changing title in hopes to motivate.

  7. #7
    Pain is fear leaving your body.... rlovebk's Avatar
    Join Date
    Aug 2008
    So. Cal.
    12F should have a much higher compression. Like double #'s you are showing. Your gauge not working correct? Opening throttle?

    Anyways the numbers are all within 10% of eachother so assuming you are not getting correct nr. from gauge they are good. If those numbers were actual ski would not run well. I believe 12F compression is 225 psi, if I remember correctly.

  8. #8
    His compression readings are like that of triple 2 strokes!

    Cam timing might be off as well.

  9. #9

    Join Date
    Aug 2009
    Shuswap lake, Canada
    You initially reported 230 compression after the re-build, so what has changed?
    Rings, valves, cam timing are possible culprits.
    It won`t develop full RPM with only 100# compression, but you likely know that already

  10. #10
    Yea. Need to get my friends snapon tester back. Im sure my cheap harbor freight one is for the junk pile. When you say cam timing, please elaborate.

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