Jetting recommendations for 760 blaster
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  1. #1
    Resident Guru soxfan1129's Avatar
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    Jetting recommendations for 760 blaster

    Iíve got a blaster, full 61x motor, bored to 760, ported cylinders and intake, factory limited pipe, msd enhancer, Ada head 165psi, picked up a set of dual 44 sbnís jetted at 110 pilot 100 main 2.5 n/s with a shiny silver spring, will that setup work or will it be way off?
    Thank you
    And yes I know 62t cases would be better off but this is the setup Iím working with


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  2. #2
    PWCToday.com Is My Home Away From Home fox river pwc's Avatar
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    Re: Jetting recommendations for 760 blaster

    OEM 44s, or???

    The jetting itself will be a good starting point, but the pop off may be too low.


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  3. #3
    Resident Guru soxfan1129's Avatar
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    Re: Jetting recommendations for 760 blaster

    Yes oem 44s, how much higher do you think I should go on the pop off?


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    PWCToday.com Is My Home Away From Home fox river pwc's Avatar
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    Re: Jetting recommendations for 760 blaster

    Stick 115gm springs in and try it.

    It is typically much easier to diagnose a pop off that is too high than one that is too low.
    2.5s with the 65gm springs you have now will put you somewhere in the 10-13psi range, if my memory is working . I've never needed to go that low with OEM 44s.....only with dual red tops or buckshots.


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  5. #5
    Resident Guru bored&stroked's Avatar
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    Re: Jetting recommendations for 760 blaster

    Its a little low on jetting for what I'd run in a superjet. I'm at 125 pilots with 115 highs. Not sure how the heavier hull will affect jetting.
    '96 Suuuperjet: 84mm 61x, ported, B-pipe, Dual 44's, Newmiller head 220psi w/girdle, Skat big hub, footholds, AMG green hell mango matte.
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  6. #6
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: Jetting recommendations for 760 blaster

    I don't understand why 2.5's/65gr with a 12psi pop-off would ever be needed
    by any application?

    Wasn't the stock 760 jetting

    135, 137.5 M
    115 L
    95gr
    1.5 N&S

    ~1 3/4 low screw
    ~1/2 hi screw


    It will not matter what the jetting is, if the impeller is the wrong size for the pipe
    and porting.


    Bill M.
    Last edited by wmazz; 11-17-2021 at 01:42 AM.
    Horsepower == Speed, RPM != Speed



  7. #7
    PWCToday.com Is My Home Away From Home fox river pwc's Avatar
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    Re: Jetting recommendations for 760 blaster

    Quote Originally Posted by wmazz View Post
    I don't understand why 2.5's/65gr with a 12psi pop-off would ever be needed
    by any application?

    Wasn't the stock 760 jetting

    135, 137.5 M
    115 L
    95gr
    1.5 N&S

    ~1 3/4 low screw
    ~1/2 hi screw


    It will not matter what the jetting is, if the impeller is the wrong size for the pipe
    and porting.


    Bill M.
    My vintage race SN ran a set of jetworks ported 61x cases with a riva (copied) ported 61x cylinder, and dual 44 red tops with a slanted intake manifold for which I can't recall the brand right now...and many other goodies, mod b-pipe, etc...

    With 14psi pop off it would lean stall and shut off about half the time when the band snapped at the race as I grabbed WOT (had a drop nozzle as well, so WOT from a standing start was possible - for those who could hold on).

    With 11psi pop off and the pop off actuator arm raised .006 above level, it would holeshot perfectly every time.

    I did a stupid amount of testing and practice with that motor set up back in the 00s.


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  8. #8
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: Jetting recommendations for 760 blaster

    Back when the only carbs were Mikuni BN round bodies or Walbro
    carbs with no jets, only adjustment screws I tried the 3 N&S combos
    available (for the BN), and stupid things like stretching or compressing
    springs and never found a benefit.

    It was common practice to increase the needle & seat when we installed
    an aftermarket flame arrestor. We replaced needle & seats to prevent lean
    seizures after engine mods (despite that a 1.5 N&S does not restrict the
    fuel pump), and if the set-up was bad, engines seized anyway.

    At PJS when customers PP 440 & 550 seized, they would bore the cylinder
    really loose, .008" or hone to .010" to .012" They called it goon clearance,
    and the engines seized despite the goon clearances. But they were not lean
    seizures caused by the fuel pump, or the N&S.

    On SBN and SBN-i carbs I prefer increasing the low jet size for acceleration.

    I also prefer high pop-off and big low jet on the family 3 seater or a race
    engine as a combination (N&S, spring, low jet, low (pilot) screw) , not as
    separate circuits.


    Bill M.
    Last edited by wmazz; 11-19-2021 at 01:14 AM.
    Horsepower == Speed, RPM != Speed



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