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  1. #1

    Join Date
    Sep 2014
    Knoxville TN

    1999 STX1100 Running Lean

    I am having a horrible time with this ski. It is running too lean, sounds like someone is hitting the front of the engine with a hammer if you pull and release the throttle rapidly. Over and over. You can hold it at 1/4 throttle all day it is seems ok. No horrible noises. I have cleaned the carbs THROUGHLY (dip tank, compressed air, etc). I have checked/clean the tank pick up. I have swapped the pulse line from the rear nipple to the front. I removed the in line fuel filter to ensure it wasnt clogged up. I am running 38 pilot, 2 turns out on low speed screw, 165 main. The needles are not worn into the slide, and the slide diaphram is not torn, no pinholes etc. The fuel pump is in good working order with no issues, I've been through it twice. I am totally stumped here and dont know what else to try. Considered swapping in a different CDI box thinking possibly timing is too advanced. Spark plugs come out whitish, not tan, brown, or even black. This ski is running the CDCV Keihin carbs. Any help/suggestions are appreciated.

    BTW, this is a brand new SBT engine. Old engine burned up the front cylinder because the vacuum cap rotted off the front pulse nipple causing an air leak.

  2. #2
    Remove the plugs and if possible take a pic of them and post it up.

  3. #3
    Are the chokes still in the carbs. They haven't been removed.

  4. #4
    Myself's Avatar
    Join Date
    May 2007
    North Central Arkansas
    Sounds like a timing issue. Verify TDC and mark PTO with a sharpie for all 3 cylinders. Use a timing light while cranking to verify same amount of advance on all three, check while running also. I have changed out several 900 and 1100 CDI's because of crapped out timing circuits. Try a #42 or 45 pilot jet at 1.5 turns out, your starter will thank you for it.

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