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 20
  1. #1
    PWCToday Guru
    Join Date
    Apr 2008
    Location
    SoCal
    Age
    46
    Posts
    364

    Carb jetting for elevation

    Are there any known formulas for jetting according to elevation? I have my jettings proper for sea level but im planning a trip that is at 6000 ft. elevation. This is for a GSXL 951cc engine. Thanks

  2. #2
    PWCToday.com Is My Home Away From Home Cliff's Avatar
    Join Date
    Jun 2011
    Location
    Where I can see the air I breathe...
    Posts
    3,892

    Re: Carb jetting for elevation

    I don't know if any formulas.

    But I think this might help:


    Sent from my iPhone using Tapatalk
    What would Chuck Norris do?

  3. #3
    Resident Guru SURFnTURF's Avatar
    Join Date
    Sep 2004
    Location
    AUSTRALIA
    Posts
    1,180

    Re: Carb jetting for elevation

    You would be better of lowering your impeller pitch so it reduces load on the engine so it can operate at the correct rev range at WOT within the correct heat range.
    Its the easiest thing to do than trying to re jet,I would grab an impeller that's at least 2 degrees less than what you have now

  4. #4
    Resident Guru JC-SuperJet's Avatar
    Join Date
    Jul 2013
    Location
    Cypress, TX
    Posts
    963

    Re: Carb jetting for elevation

    At +6000 ft elevation, aprox. 2000 meter is the reference chart point which indicates only a 2.5 reduction in Main Jet Size.

    You can easily compensate by turning the High Speed Adjuster Screws IN to lean out the mixture. No need to rejet at that elevation.

    Use a good Tachometer to fine tune the carbs.

  5. #5
    Resident Guru JC-SuperJet's Avatar
    Join Date
    Jul 2013
    Location
    Cypress, TX
    Posts
    963

    Re: Carb jetting for elevation

    However, at +6000ft elevation there is a corresponding drop in atmospheric pressure of 3 psi (from 14.7 psi at sea level to 11.7 psi at 6000 ft) which will affect pop-off pressure requirements.

    "Pilots who fly at high altitudes (1,200m MSL/4,000' MSL and above) may want to adjust the pop-off pressure by adding shims to the existing spring or replacing the spring with one of greater compression strength"

    Apparently, a stronger spring is needed to make-up for the extra 3 psi needed of pop-off pressure.

    Need someone who rides regular at +6000 ft to let us in on the pop-off adjustment...

  6. #6
    Resident Guru JC-SuperJet's Avatar
    Join Date
    Jul 2013
    Location
    Cypress, TX
    Posts
    963

    Re: Carb jetting for elevation

    I think the 947 seadoo carbs high speed adjustments are set at zero turns out? If so, then downsize main jets while you're swapping springs...
    Last edited by JC-SuperJet; 06-04-2017 at 05:13 AM.

  7. #7
    PWCToday Guru
    Join Date
    Apr 2008
    Location
    SoCal
    Age
    46
    Posts
    364

    Re: Carb jetting for elevation

    Thank you for the mikuni chart Cliff. good enough formula for me.

    SurfNturf, impeller is a great idea, maybe ill do both. Have plenty of time to prepare

    JC, the chart is in -Ft. and not in -Meter. Its a bit blurry so i googled for more images and found a higher resolution one. With that said 6000 ft elevation calls for an 8 points change, but what i dont like is it figures only for the HS circuit... i do like the idea of going with a heavier spring to compensate for the atmospheric pressure. I may try that along with 5 points less on the HS jet

    Yes we need someone from like UT or CO to chime in
    Last edited by Spades; 06-04-2017 at 09:44 AM.

  8. #8
    PWCToday.com Is My Home Away From Home Cliff's Avatar
    Join Date
    Jun 2011
    Location
    Where I can see the air I breathe...
    Posts
    3,892

    Re: Carb jetting for elevation

    Spades,

    Is this a stock 951cc engine?


    Sent from my iPhone using Tapatalk
    What would Chuck Norris do?

  9. #9
    Resident Guru JC-SuperJet's Avatar
    Join Date
    Jul 2013
    Location
    Cypress, TX
    Posts
    963

    Re: Carb jetting for elevation

    Ooops...looks like I need new reading glasses...

  10. #10
    PWCToday Guru
    Join Date
    Apr 2008
    Location
    SoCal
    Age
    46
    Posts
    364

    Re: Carb jetting for elevation

    Quote Originally Posted by Cliff View Post
    Is this a stock 951cc engine?
    Just has flame arresters and disabled accelerator pump, and rejetted accordingly

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