pxctoday

» Log in

User Name:

Password:

Not a member yet?
Register Now!

» Find OEM Parts

» wallpapers

Page 1 of 2 12 LastLast
Results 1 to 10 of 15
  1. #1
    PWCToday Newbie mrfisherman42's Avatar
    Join Date
    Apr 2007
    Location
    Missouri
    Posts
    5

    adjusting Mikuni Super BN carbs.

    Hi, I just got a 1994 Sea Doo XP that has Mikuni Super BN carbs on it. I know alot about regular engines but nothing about 2 stroke PWC engines. This has a huse dead spot when you try to give it fuel the idols perfect but as soon as you try to give it any fuel it just falls over and dies. Any suggestions would be great appreciated.

  2. #2
    PWCToday Newbie mrfisherman42's Avatar
    Join Date
    Apr 2007
    Location
    Missouri
    Posts
    5

    Re: adjusting Mikuni Super BN carbs.

    Sorry I just read my post and I will learn to preview it first now because my typing is terrible.

  3. #3
    I dream skis astral's Avatar
    Join Date
    Dec 2003
    Location
    Knoxville TN
    Age
    36
    Posts
    663

    Re: adjusting Mikuni Super BN carbs.

    time for a carb clean!! The jets are 0 highs and lows 1-1/4 - 1-1/2

  4. #4
    PWCToday Newbie mrfisherman42's Avatar
    Join Date
    Apr 2007
    Location
    Missouri
    Posts
    5

    Re: adjusting Mikuni Super BN carbs.

    Man I hate to sound dumb but that was all greek to me. Do I need to remove them to do this or is it adjustable on the wave runner? Than ks for the help.

  5. #5
    I dream skis astral's Avatar
    Join Date
    Dec 2003
    Location
    Knoxville TN
    Age
    36
    Posts
    663

    Re: adjusting Mikuni Super BN carbs.

    To clean the carbs they have to be removed . This is ult.what you will have to do.To adjust the jets you can do this without removing the carbs.There will be three screws on the carb top screw is high speed bottom screw is low speed and there will be another adjustment screw beside the low speed that is the idle adjustment.Find the low speed screw and turn it all the way in,Then back it out 1-1/2 turns on the carbs.Make shure the high is at zero turns out(all the way in).It may be nes for you to use a mirror to see the screws,also it is alot easier if you remove the air box.

  6. #6
    I dream skis Dan750SX's Avatar
    Join Date
    Jul 2005
    Location
    Colorado
    Age
    35
    Posts
    505

    Re: adjusting Mikuni Super BN carbs.

    I just got a Mikuni Super BN 44 and have some questions.

    First, I wanted to figure out which jets were factory installed. Unfortunately, after getting the regulator cover off, one of those incredibly torqued in Philips screws covering the jets stripped out. So looks like I need a screw remover. But anyway...

    I'm pretty sure I'll have to re-jet, given I'm at about 6000' elevation. How many sizes larger and smaller than what I have installed should I get?

    Also, some questions about the tuning process. There are two parts of the Mikuni tuning procedure which I don't get.

    First:

    Remember, the low speed adjuster is only for adjusting the idle mixture. If you use the adjuster to help get rid of a low speed hesitation, you will probably find that your engine will load up in no wake zones, or after extended idling.
    What do they mean by "load up"? Do the revs drop or increase when an engine "loads up"?

    Next:

    Low speed jet excerpt:
    Ride the boat at a constant 1/4 throttle opening for about 1 minute and then quickly open the throttle fully, there should be no hesitation and the engine should not show signs of being loaded up. If it hesitates, it's lean; if it's loaded up, it's rich.
    And in the high speed jet adjustment:
    The procedure for testing for the correct high speed jet size is the same as for the low speed, except that you should now hold the throttle at a constant 1/2 open for one minute, then quickly open the throttle fully to check the engine response. If the engine hesitates, the carb is lean. If the engine takes a second or two to clear out and then accelerate, the carb is too rich.
    Okay, what's the difference between the engine hesitating, and the engine taking "a second or two to clear out and then accelerate"? It sounds like the same thing to me. In the low speed adjustment, it said that the engine should not hesitate, or show signs of being "loaded up". (there's that loading word again)

    Can somebody shed some light on this?

    Thanks!

    Edit: In case anybody is wondering, the excerpts are from the Super BN Manual found here:
    http://www.mikuni.com/pdf/sbn_manual.pdf
    Last edited by Dan750SX; 05-15-2007 at 08:01 PM.
    Dan White
    1993 Kawi 750SX

  7. #7
    PWCToday.com Is My Home Away From Home Matt_E's Avatar
    Join Date
    May 2004
    Location
    Blowing up Motors
    Posts
    12,071

    Re: adjusting Mikuni Super BN carbs.

    Loading up - it starts out running fine, may drop a bit in RPM, and then has trouble taking off (after extended idle).

    Lean hesitation: you pull the throttle, and the boat falls on its face, stumbles, and picks right back up.

    Rich hesitation, or having to clear out: the engine does not stumble, but reacts slowly to the throttle input and slowly climbs out of the RPM hole.
    If I sound like a moron, it's only because I haven't typed enough words yet.

    Jetworks....Blowsion....Superfreak!....Thrust Innovations

  8. #8
    PWCToday.com Is My Home Away From Home 1goofball's Avatar
    Join Date
    Jun 2006
    Location
    Golden Gulf Coast, MS.
    Posts
    2,492

    Re: adjusting Mikuni Super BN carbs.

    * mrfisherman * if cleaning carbs don't work, I bet it is the stator. Mine acted like you said and stator was fried. Replaced and now runs good.

  9. #9
    I dream skis bluffskier's Avatar
    Join Date
    May 2006
    Location
    Texas
    Posts
    618

    Re: adjusting Mikuni Super BN carbs.

    Quote Originally Posted by Matt_E
    Rich hesitation, or having to clear out: the engine does not stumble, but reacts slowly to the throttle input and slowly climbs out of the RPM hole.

    I think my Superjet is alittle rich then.

  10. #10
    I dream skis Dan750SX's Avatar
    Join Date
    Jul 2005
    Location
    Colorado
    Age
    35
    Posts
    505

    Re: adjusting Mikuni Super BN carbs.

    Quote Originally Posted by bluffskier
    I think my Superjet is alittle rich then.
    Better to be a little rich than a little lean, at least as far as the high speed jet and screw is concerned. Lean can lead to piston seisures. Rich just causes hesitation.

    Personally, once I find my ideal high speed setting, I'll adjust it about 1/8 to 1/4 turn rich just to be sure.
    Last edited by Dan750SX; 05-16-2007 at 01:12 AM.
    Dan White
    1993 Kawi 750SX

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