Starting point for jetting?

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  1. #1
    Frequent Poster
    Join Date
    Sep 2017
    Rochester Ny

    Starting point for jetting?

    Got some 46 Blackjacks (annular discharge) for a kawi 1100 engine we built.

    Can someone give me atleast a starting point for these? Are they reverse jetting?

    Kaw 1100
    vforce 3
    7 degree timing
    dried stock exhaust
    boyesen intake
    ada head 150lb comp

  2. #2 Is My Home Away From Home wmazz's Avatar
    Join Date
    Jul 2013
    Riverside, CA
    Blog Entries

    Re: Starting point for jetting?

    I am curious what changes you made with the porting? Not specs,
    just general stuff.

    Here is a starting point, I have not tried the specs. These specs are
    intended as a way to learn jetting and tuning. Use my blog as a general
    guideline. If you spend the time to dial it in, the specs could be converted
    to better reverse jetting (using the blog).

    1.5 seat
    80gr spring
    120 low
    135 main
    3/4 low speed (pilot) screw.
    1 1/4 hi speed screw.

    The needle & seat, spring, low jet, and pilot screw are a combo, and
    they are easier to dial in when you treat them as a group, compared
    to treating them as 4 individual circuits or some arbitrary pop-off.

    Trust the standard needle&seat spring combos like an 80gr spring
    and 1.5 or 2.0 seat.
    For that reason, you could keep the 2.0 seat, but it
    will not prevent a seizure or provide a noticeable advantage because it is
    a larger seat.

    Lower pop-offs only makes diaphragm carbs run sloppier.

    Always start with your low jets because the pilot and low speed circuits
    overlap with the mains. The idle drop test will dial in your low speed jet

    If the engine will start and idle with the pilot screws closed, decrease the
    low speed jet ~2 sizes, and turn out the pilot screw 1/2 to 3/4 of a turn and
    re-test using the idle drop test.

    Even the mains might be too rich, but because your carbs don't have the
    main jet booster (bomb sight) and they will not draw as much fuel as the
    stock main jet booster. For that reason I wanted to be safe as possible.

    If they are rich, drop the mains 2 sizes and turn out the hi speed screw
    3/4 turns and keep testing.

    Bill M.

    Keep in mind cold water and air temps require more fuel.

    Good carb base gaskets will help insure your low speed jetting is accurate.

    If you have a speed plate, make .062" gaskets from rubberized felt.
    Last edited by wmazz; 11-26-2021 at 08:10 PM.
    Horsepower == Speed, RPM != Speed

  3. #3
    Frequent Poster mjkaliszak's Avatar
    Join Date
    Mar 2009

    Re: Starting point for jetting?

    Last edited by mjkaliszak; 12-01-2021 at 08:56 AM.

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