Page 1 of 4 1 2 3 ... LastLast
Results 1 to 10 of 31
  1. #1
    BlueFishCrisis's Avatar
    Join Date
    Aug 2011
    Location
    Medina, Ohio, United States
    Posts
    4,988
    +1
    140

    How to rebuild Mikuni SBN 38 Triple Carbs

    This thread will describe how to rebuild the Mikuni SBN 38 Triple carbs found on all Polaris Fuji Engines. Note that the 650, 750, and 780 versions are all the same, with a few minor variations I will point out.

    Carb kits can be obtained from many different sources. Ensure that only Genuine Mikuni parts are used. For this thread, the carb kit was obtained from John Zigler at Watcon.com. At the time of this post, the kit was $150 USD plus shipping.

    The parts included in this kit are 3 ea o rings for the high and low speed adjusters, 3 ea needles and seats (size 2.0), 3 ea springs (size 80 gram), 3 ea clear check valves, 3 ea filters, and 3 ea diaphragms.

    Here is a layout of typical tools and supplies needed for the rebuild:

    Click image for larger version. 

Name:	001 Tools and parts.jpg 
Views:	350 
Size:	70.0 KB 
ID:	331802

    Carb cleaner, multipurpose spray lubricant, small and large phillips, small and large flat heads, scraper, 2 stroke oil, and paper towels. I also used various small pics and brushes as you will see throughout the photos.
    Last edited by BlueFishCrisis; 06-09-2014 at 11:08 AM.


  2. #2
    BlueFishCrisis's Avatar
    Join Date
    Aug 2011
    Location
    Medina, Ohio, United States
    Posts
    4,988
    +1
    140
    Start by unbolting the carbs from the intake manifold.

    Click image for larger version. 

Name:	000 remove carb nuts.jpg 
Views:	218 
Size:	99.4 KB 
ID:	331803

    Once you have the carbs off, remove the screws holding the alignment plate to the 3 individual carbs.

    Click image for larger version. 

Name:	003 Remove alignment plate.jpg 
Views:	235 
Size:	102.1 KB 
ID:	331804

    You will also need to loosen the spring loaded linkages between the carbs connecting the throttle plates and the choke plates.

    Click image for larger version. 

Name:	076 tighten linkage.jpg 
Views:	202 
Size:	83.7 KB 
ID:	331805Click image for larger version. 

Name:	077 tighten linkage.jpg 
Views:	238 
Size:	116.7 KB 
ID:	331806

  3. #3
    BlueFishCrisis's Avatar
    Join Date
    Aug 2011
    Location
    Medina, Ohio, United States
    Posts
    4,988
    +1
    140
    Next, remove the fuel inlet cover. Pay attention to which cover comes off of each of the various locations ( MAG, CEN, PTO). The covers are different for each location, and may vary based on year and motor size. All, however, are interchangeable and will work on any version.

    Click image for larger version. 

Name:	004 Remove fuel inlet cover.jpg 
Views:	211 
Size:	106.0 KB 
ID:	331812

    Remove the fuel filter, and discard.

    Click image for larger version. 

Name:	005 remove fuel filter.jpg 
Views:	208 
Size:	87.0 KB 
ID:	331813Click image for larger version. 

Name:	006 discard old filter.jpg 
Views:	175 
Size:	88.5 KB 
ID:	331814

    Remove the black rubber gasket. Keep this as long as it is in good condition. The kit does not come with a replacement.

    Click image for larger version. 

Name:	007 remove inlet gasket.jpg 
Views:	191 
Size:	78.3 KB 
ID:	331815

  4. #4
    BlueFishCrisis's Avatar
    Join Date
    Aug 2011
    Location
    Medina, Ohio, United States
    Posts
    4,988
    +1
    140
    Before removing the adjuster needles, you can count how many turns it takes to screw each of them in so they are fully seated. Record this measurement for each carb, each screw. When it its time to Re-assemble, you now have documentation on where they were. Or, you can reset to factory settings.

    Next remove the low speed adjuster. Note the o ring. If the adjuster comes out without one attached, you will need to reach in with a small pick and retrieve it. Often the washer stays in place covering the o ring as it is painted after it is installed.

    Click image for larger version. 

Name:	008 remove low speed screw.jpg 
Views:	199 
Size:	88.1 KB 
ID:	331818Click image for larger version. 

Name:	009 note rubber o ring on lows.jpg 
Views:	221 
Size:	52.3 KB 
ID:	331819

    Remove the blue cap on the high speed adjuster with a pair of needle nose pliers. I choose to discard these and not re-install after the rebuild.

    Click image for larger version. 

Name:	010 remove cap on high speed.jpg 
Views:	201 
Size:	102.0 KB 
ID:	331820

    Remove the high speed adjuster, keeping an eye out for the o ring.

    Click image for larger version. 

Name:	011 remove high speed.jpg 
Views:	198 
Size:	96.0 KB 
ID:	331821
    Last edited by BlueFishCrisis; 08-18-2014 at 10:55 AM.

  5. #5
    BlueFishCrisis's Avatar
    Join Date
    Aug 2011
    Location
    Medina, Ohio, United States
    Posts
    4,988
    +1
    140
    Flip the carb body over, and remove the diaphragm cover with 4 phillips head screws. Note these have lock washers on them that need to be retained.

    Click image for larger version. 

Name:	012 remove diaphragm cover.jpg 
Views:	158 
Size:	74.4 KB 
ID:	331822Click image for larger version. 

Name:	013 expose old diaphragm.jpg 
Views:	180 
Size:	85.5 KB 
ID:	331823

    Remove old diaphragm.

    Click image for larger version. 

Name:	013 expose old diaphragm.jpg 
Views:	180 
Size:	85.5 KB 
ID:	331823Click image for larger version. 

Name:	014 remove old diaphragm.jpg 
Views:	166 
Size:	79.7 KB 
ID:	331824Click image for larger version. 

Name:	015 diphragm removed.jpg 
Views:	197 
Size:	103.0 KB 
ID:	331825

  6. #6
    BlueFishCrisis's Avatar
    Join Date
    Aug 2011
    Location
    Medina, Ohio, United States
    Posts
    4,988
    +1
    140
    Next, remove the screw holding the lever arm pin. This may be corroded and tough to remove. Use lots of downward pressure when removing. You can also use an impact screwdriver to assist in removal of any of the screws in the carb. It is essential to remove the fuel inlet cover first, so the carb will lay flat on the bench when trying to remove these screws.

    Click image for larger version. 

Name:	016 remove screw retaining lever arm.jpg 
Views:	251 
Size:	89.0 KB 
ID:	331828

    Next, remove the lever arm, pin, and needle.

    Click image for larger version. 

Name:	017 remove lever arm and pin.jpg 
Views:	164 
Size:	75.5 KB 
ID:	331829Click image for larger version. 

Name:	018 lever and needle removed.jpg 
Views:	184 
Size:	46.2 KB 
ID:	331830

    Note the spring that remains when the arm is removed. This spring will need to be retained for 780 carbs, as the replacement provided is for the 650 and 750 models. If you are rebuilding a 650 or 750 set, discard the springs.

    Click image for larger version. 

Name:	019 note spring under arm.jpg 
Views:	178 
Size:	71.5 KB 
ID:	331831

  7. #7
    BlueFishCrisis's Avatar
    Join Date
    Aug 2011
    Location
    Medina, Ohio, United States
    Posts
    4,988
    +1
    140
    Here we will remove the seat retaining screw. This compresses a small plate the holds the seat firmly in place.

    Click image for larger version. 

Name:	020 remove seat retainer screw.jpg 
Views:	159 
Size:	94.8 KB 
ID:	331832Click image for larger version. 

Name:	021 remove seat retainer plate.jpg 
Views:	188 
Size:	79.9 KB 
ID:	331833

    With those removed, use a pair of needle nose pliers to grip and remove the seat. Pull straight up with a decent amount of force. The more corroded your carbs, the more difficult it will be to remove. PB Blaster or similar may help in removal.

    Click image for larger version. 

Name:	022 remove seat.jpg 
Views:	154 
Size:	84.2 KB 
ID:	331834Click image for larger version. 

Name:	023 seat removed.jpg 
Views:	174 
Size:	88.0 KB 
ID:	331835

  8. #8
    BlueFishCrisis's Avatar
    Join Date
    Aug 2011
    Location
    Medina, Ohio, United States
    Posts
    4,988
    +1
    140
    Next, remove the screws holding the valve body assembly in place. Lift off the valve body assembly with pliers. You may need to wiggle it a bit due to corrosion.

    Click image for larger version. 

Name:	024 remove screws to access jets.jpg 
Views:	156 
Size:	100.2 KB 
ID:	331836Click image for larger version. 

Name:	025 remove jet cover.jpg 
Views:	146 
Size:	99.1 KB 
ID:	331837Click image for larger version. 

Name:	026 cover removed.jpg 
Views:	163 
Size:	97.1 KB 
ID:	331838

    Remove the rubber valve body gasket and retain for reinstallation.

    Click image for larger version. 

Name:	027 remove rubber gasket.jpg 
Views:	178 
Size:	94.6 KB 
ID:	331839

  9. #9
    BlueFishCrisis's Avatar
    Join Date
    Aug 2011
    Location
    Medina, Ohio, United States
    Posts
    4,988
    +1
    140
    Remove the low speed jet using the small flat head screwdriver. Find a screw driver that just fits inside the hole for the jet. Remember the jets are brass and therefore a softer metal. The larger the blade you use, the better chance you will NOT cause damage to the jet.

    Click image for larger version. 

Name:	028 remove low speed jet.jpg 
Views:	172 
Size:	104.8 KB 
ID:	331840Click image for larger version. 

Name:	029 low speed jet removed.jpg 
Views:	151 
Size:	61.2 KB 
ID:	331841

    Remove the high speed jet.

    Click image for larger version. 

Name:	030 remove high speed jet.jpg 
Views:	157 
Size:	83.7 KB 
ID:	331842Click image for larger version. 

Name:	031 high speed jet removed.jpg 
Views:	156 
Size:	93.8 KB 
ID:	331843

    Retain the jets for re-installation. The size of the jets are imprinted on top of the jet next to the screwdriver slot for the high speed, and on the side of the jet for the lows. Ensure you have the proper jets for your ski, especially if you bought the carbs separate from the ski. Reference your owners manual for the correct sizing.

  10. #10
    BlueFishCrisis's Avatar
    Join Date
    Aug 2011
    Location
    Medina, Ohio, United States
    Posts
    4,988
    +1
    140
    Now that the old carb is completely disassembled, it is time to clean it. Be sure to use spray carb cleaner and compressed air to clean it out. Others prefer a full carb bath and small gauge wire to clean out the passages. Ensure every nook and cranny is clean and corrosion free, including the jets themselves.

    Click image for larger version. 

Name:	032 clean carb body.jpg 
Views:	185 
Size:	64.7 KB 
ID:	331844

    You may need to use a wire brush and or picks to clean out corrosion.

Page 1 of 4 1 2 3 ... LastLast

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Anyone live in Southern Cal that can teach me how to rebuild my carbs on 1200xl ltd
    By Rookiepwc in forum Yamaha PWC Performance (2-stroke)
    Replies: 3
    Last Post: 09-11-2013, 04:47 PM
  2. How to rebuild stock 99 ultra carbs?
    By screamindemon in forum Kawasaki PWC Performance (2-stroke)
    Replies: 16
    Last Post: 08-03-2011, 09:44 PM
  3. Can someone post a how-to on how to remove mikuni carbs from an xl800?
    By ctheodores in forum Yamaha Open Discussion
    Replies: 3
    Last Post: 03-18-2010, 04:00 AM
  4. help...carb throttle shaft sbn 38 triple
    By johnson7454 in forum Yamaha Old School Skis
    Replies: 8
    Last Post: 10-17-2008, 11:20 AM
  5. Manual on how to rebuild Carb?
    By TomToro in forum 2-Stroke Performance
    Replies: 4
    Last Post: 07-27-2008, 06:51 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •