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  1. #1

    Whats the best way to tune a carb?

    I was messing with the carb on my Sl650, and from what i see its running alot better. I originally put the screws to about where they were before i rebult the carb, but it still ran like crap and needed choke.

    Well, i think its running alot better, but there is no way to tell until i get it into water. So, my question is, whats the best way to tune a carb?

    Do i turn all 3 high adjustment screws at the same time until i think its running best and leave it there, or what? Leave it attached to the trailer? Would there be a reason to turn one carbs screw more than another? Do the low adjustment screws matter other than idle?
    Last edited by ZOMGVTEK; 06-10-2008 at 06:36 PM.

  2. #2
    Moderator beerdart's Avatar
    Join Date
    Aug 2006
    From the tech section.


    Start with the screws set at 1 turn out, and tune with the tachometer for peak Rpm, then stop there and count the number of turns on the high speed screws. Write this down on a piece of paper.. Then turn the high speed screws in all the way and open them to 1/4 turn open. (Now you will be testing starts only, so no more big high rpm trips around the course). You are only turning in the high speeds to allow you to easily tune the low speeds.

    Now check the low speed screws and set them at 1 turn and do a practice start; To test the low speed setting pretend that you just jumped the start and you have to start with no holder. Hold the ski by yourself and hold as many Rpm as you can (don't blow it out first for testing) and then nail the throttle hard.... NO FARTHER THAN 50 FEET, as you are only testing the start response

    If it blubbers like a schoolgirl trying to guzzle a quart of beer, then it's too rich on the low speed screws..
    If it falls flat on the line (like someone punched you in the stomach).. It's too lean on the low speed screws.

    When you like the acceleration off the line, stop there and count the number of turns on the low speed screws. Write this down on a piece of paper.. Then re-set your high speed screw where they show the best peak Rpm earlier and try both a start and a peak Rpm run...
    It will probably "blubber" a little off the line... DO NOT turn in the low speed screws... Instead, go back out on the course and fine tune for peak Rpm again.. The blubbering off the line is caused by having too much fuel in the high speed circuit... Write down your new high speed setting on the piece of paper along with the best low speed setting that you found earlier, this will be your base-line carburetor settings.
    If the high or low speed screws are open more than 11/4 turns, then you need to swap to the next bigger jet.
    If the high or low speed screws are closed all the way, then you need to change to the next size smaller jet.

  3. #3
    ph2ocraft's Avatar
    Join Date
    Apr 2006
    Campbell, Ca.
    I was just typing, check the tech section and use the awesome tuning tips by Randy at Watcon titled "Tuning for Girls" It works awesome, I still reference it to this day.

  4. #4
    Great, i guess my tach i bought is going to come in handy then. Ill wait until it comes in and then go out for a test and tune session... This time with a gps...

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