750SXI Pro Pop-off question
pxctoday

» Log in

User Name:

Password:

Not a member yet?
Register Now!

» Find OEM Parts

» Jobs

» wallpapers

Page 1 of 2 12 LastLast
Results 1 to 10 of 13
  1. #1
    PWCToday Newbie Corndog69's Avatar
    Join Date
    Feb 2017
    Location
    Caledonia
    Age
    49
    Posts
    39
    Blog Entries
    1

    750SXI Pro Pop-off question

    I know this has been debated several times - but here goes anyway. Need everyones thoughts about my 1998 SXI Pro pop-off settings.

    Ski currently has:
    * Stock size pistons (new)
    * Factory Limited Wet Pipe
    * K&N Carbs
    * ADA head (compression around 170)
    * Lightened flywheel (newmiller)
    * Stock Jets - 147.5 (high speed) and 75 (low speed)
    * Stock needle & seat 1.5
    * stock spring
    * New rebuild on carbs - both set at 30psi pop off

    Factory Pipe says that #80 jet might be a better pilot jet. I would like everyones thoughts about using a 2.0 needle and seat and keeping the jets stock? The reason I'm asking is because I cooked one of the cylinders of my 1 year rebuild and blew out a quarter size piece of the top (outside edge) of the piston. The first cylinder in line looks/is perfect but the second one (front cylinder) is the one that got hot. Exact same carb settings on both carbs - who woulda' guessed......

    The motor is back at Flannery Motorsports to get rebuilt, and I rebuilt the carbs last night. I'm second guessing myself now about pop-off pressure, springs, Needle/seat, and jet sizes. please provide your thoughts as need to get it 100% correct this time.

    Thank you.

  2. #2
    PWCToday.com Is My Home Away From Home mcn6's Avatar
    Join Date
    Apr 2006
    Location
    Oregon
    Age
    62
    Posts
    3,285

    Re: 750SXI Pro Pop-off question

    Not sure with K&N flame arrestors, but with PROK or Tau-Ceti I would start with:
    152.5 main jets
    80 pilot jets
    2.0 N/S
    80g springs



    Home of Newmiller Machine

  3. #3
    PWCToday.com Is My Home Away From Home bandit88's Avatar
    Join Date
    May 2014
    Location
    Green Bay WI
    Age
    32
    Posts
    2,170

    Re: 750SXI Pro Pop-off question

    I have a similar setup, except for SP cylinder and im running the stock flame arrestor with the trumpets removed. I found that stock needle/seat and spring work best. Not sure how much of a difference there is between the two flame arrestors when it comes to intake vacuum.
    Last edited by bandit88; 08-19-2019 at 04:15 PM.
    -95 750SXI
    -86 440 with PJS800 conversion (now 650) - http://www.pwctoday.com/showthread.php?t=466927
    -92 750SS
    -81 JS440
    Parts for sale HERE

  4. #4
    Attention ***** PWCToday.com Is My Home Away From Home JonnyX2's Avatar
    Join Date
    Jun 2006
    Location
    Sin City USA
    Age
    57
    Posts
    30,360

    Re: 750SXI Pro Pop-off question

    2.0NS
    80g
    80p
    150-152.5m
    Quote Originally Posted by Firebird A/C&Heating View Post
    OMG.....Rules for 550 vintage ski class...550 ski riders do not conform to any kind of rules. That is why you are riding a 550 ski in the first place. Rules suck....
    PS...the rule book will be in my 550 pump
    Quote Originally Posted by WB1994
    Listen , stop your cryin' , its only an X2.

  5. #5
    PWCToday Newbie Corndog69's Avatar
    Join Date
    Feb 2017
    Location
    Caledonia
    Age
    49
    Posts
    39
    Blog Entries
    1

    Re: 750SXI Pro Pop-off question

    Thanks. What is a good pop off pressure to achieve for strong take offs? I like wave jumping on the lake more than WOT all the time (I’m old ).

  6. #6
    PWCToday Newbie Corndog69's Avatar
    Join Date
    Feb 2017
    Location
    Caledonia
    Age
    49
    Posts
    39
    Blog Entries
    1

    Re: 750SXI Pro Pop-off question

    BEULER.....BEULER....BEULER??? Any thoughts out there

  7. #7
    PWCToday Newbie Corndog69's Avatar
    Join Date
    Feb 2017
    Location
    Caledonia
    Age
    49
    Posts
    39
    Blog Entries
    1

    Re: 750SXI Pro Pop-off question

    OK, I installed the recommended parts:
    * 152.55 main jets
    * 80 pilot jet
    * 80 gram spring
    * 2.0 needle / seat

    A lot of surveying said this was the best combination for my setup. Wondering if anyone knows a safe starting point for low and high speed screws? Is the second carb usually opened up more than the first one with the pump? I had them set identical the first time and dried up the front cylinder.... thanks.

  8. #8
    PWCToday.com Is My Home Away From Home mcn6's Avatar
    Join Date
    Apr 2006
    Location
    Oregon
    Age
    62
    Posts
    3,285

    Re: 750SXI Pro Pop-off question

    Set both needles at 1.5 turns out. This should put you in the safety zone and it will probably be a little rich so plan on adjusting the needles to fine tune. Once you get to your ride spot simply follow the tuning instructions as outlined in the Mikuni SBN Owners Manual.
    https://www.mikuni.com/pdf/sbn_manual.pdf



    Home of Newmiller Machine

  9. #9
    PWCToday Newbie Corndog69's Avatar
    Join Date
    Feb 2017
    Location
    Caledonia
    Age
    49
    Posts
    39
    Blog Entries
    1

    Re: 750SXI Pro Pop-off question

    The carbs are back together and both are at 13psi pop-off pressure. Seems low to me - will that make for good take-offs and wave jumping?

  10. #10
    Attention ***** PWCToday.com Is My Home Away From Home JonnyX2's Avatar
    Join Date
    Jun 2006
    Location
    Sin City USA
    Age
    57
    Posts
    30,360

    Re: 750SXI Pro Pop-off question

    The number is not important. It is the throttle response produced that matters
    Quote Originally Posted by Firebird A/C&Heating View Post
    OMG.....Rules for 550 vintage ski class...550 ski riders do not conform to any kind of rules. That is why you are riding a 550 ski in the first place. Rules suck....
    PS...the rule book will be in my 550 pump
    Quote Originally Posted by WB1994
    Listen , stop your cryin' , its only an X2.

Page 1 of 2 12 LastLast

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Powered by vBadvanced CMPS v4.2.0