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  1. #1

    Running on one cylinder at idle

    My motor was only running on one cylinder so I rebuilt the carbs. I thought I did a good job with the cleaning the carbs, taking out the high and low speed Jets and putting the whole carb in a gallon of carburetor cleaner and blowing it out with compressed air. I put it back together and it is still running on one cylinder when I crank it up. I hit the gas and it will bog down for a second and as it starts to pick up rpm's it finally will pick up all cylinders and run on all 3. It's getting spark and it's getting fuel. The spark plug wires are not grounding on anything, I checked that. I'm think maybe adjust the carbs? I'm nit sure and help would be great. It's running on the center cylinder at idle. Also when I add choke it just dies. Thank you for your help.

  2. #2
    Resident electronics hacker UnityRacing's Avatar
    Join Date
    May 2007
    Suffolk, VA
    Are you certain it is getting spark on all 3 at idle? Did you use an inline spark tester to verify? Have you tried new plugs?

    Have you tried to dribble some fuel down the carb on the 2 suspect cylinders? Should run for 20 seconds or so that way. Or at least sound better for a few seconds.

    Did you actually rebuild the carbs or just dunk em in carb cleaner? That's not the best method. The dunking is something you do after a full disassembly and let them sit overnight followed by installing a rebuild kit. Make sure you check and adjust the pop off pressure.

  3. #3
    Thanks for your response.. I did use a tester and they are brand new spark plugs gapped according to the manual. I even took out the plugs to see if it was sparking with the engine on and it was. I did try to pour raw fuel in the top of both of the carbs and it wouldn't rev up or fire on them at that time either... I did use 3 fresh new kits to rebuild the carbs. I took them all the way down, low speed jet and high speed jet was taken out... I'm not sure what pop off pressure is.... I'm stumped....

    also so when I add full choke the engine just dies.... Maybe the carbs are out of sync?

  4. #4
    Resident electronics hacker UnityRacing's Avatar
    Join Date
    May 2007
    Suffolk, VA
    I'm more of a DI guy, so I'm going to stop here before I give you wrong info. I figured nobody else had chimed in so I would give you some of the basics.
    Pop off pressure is the amount of fuel pressure it takes to pop the needle off the seat. You can't just rebuild a carb using the rebuild kit, you have to take the spring and compress or stretch it a bit to get the pressure right.
    This may or may not apply to your carbs, you will have to watch some youtube videos to see what I mean, and then compare against your carbs to see if you have a similar setup. There are 2 major brands of watercraft carbs - Mikuni and Kehin (sp?).
    My boat uses 6 Mikuni's so that's what I'm mostly versed in. I'm not sure what Polaris uses as all my Polaris skis are fuel injected.

  5. #5
    CliffsidePM's Avatar
    Join Date
    May 2014
    Racine, WI

    What is the year, model and history of the ski? Have you own it or just got it? Did it run correct before. When did it start acting up? A good battery is a must. It has to have over 10.6 volts while cranking to spark correctly. Did you check your compression? what are they?


  6. #6

    Join Date
    Jun 2015
    Check your compression and also check the gap of your spark plugs (might try a hotter heat range, they might be fouling out at idle.)

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