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  1. #1

    How to rebuild stock 99 ultra carbs?

    Haven't ventured into rebuilding ultra carbs before, so wondering if this process is documented anywhere, or if anyone has any tips they would be willing to share?

    I'm consistently fogging the plug in the cylinder closest to stern (which I guess is considered Cylinder #3?)... Even if I can get it running on all 3, it will hold 6200rpm at WOT for a minute or two, then fall down to 4000 rpm, max with stern facing cylinder stone cold and plug clean as a whistle...

    Any special tools required to do this?

    Thanks all!!!!

  2. #2
    Buy a rebuild kit off ebay or similar. It will come with all the gaskets, diaphragms, etc. that you should need. They are usually cheaper than piece by piece.

    I have never worked on an ultra carb, but if it is a typical keihin carb I can't think of any special tools you will need except a screw driver, carb cleaner, and maybe a few sockets.

  3. #3
    thanks. sounds straight forward enough... just wish there were some step by step photos to follow as this will be my first time wrenching on them...

  4. #4
    witness140's Avatar
    Join Date
    Aug 2010
    Not sure I understand. You are "fogging" #3......does this mean fouling? Yet it is clean as a whistle on a plug chop?

  5. #5
    Just remember how it was in there when you were taking it apart and put it back that way. When I pull transmissions and/or engines out of cars and do work on them, I will often take pictures as I go so I can reference them to know where things go back.

    As far as what to do, while your in there just look for any build up and lightly scrape it off being sure not to scratch any severe groves into the surface. Look at all the diaphragms, gaskets, etc. for tares/holes. Unscrew the jets and spray the carb cleaner through the hole to clear out any debris. Before reassembling, thoroughly spray carb cleaner through every orophice you can find to ensure no debris is in there. Just a small particle of dirt can clog a jet causing performance problems.

    I have some photos of my carb apart that I can upload when I get home so you can at least see what is on the inside.

    P.S. a carb rebuild might not be what you are in need of if you are just smoking really badly or if the plugs are constantly oil fouling. Smoke/ oil fouled plugs is often a sign that you need to do some rejeting because you are running rich.

  6. #6
    Quote Originally Posted by witness140 View Post
    Not sure I understand. You are "fogging" #3......does this mean fouling? Yet it is clean as a whistle on a plug chop?
    thanks, you're right, i meant fouling, not fogging...

    when i take the plug out its clean, not dripping with oil... its a little wet, but not all black and its not soaking wet either, nor is it gunked up.. the plugs in the ski are bran spankin new, and this one in particular looks nice and clean, just a bit wet... the others appear a mixture of tan and white...these plug conditions are after running 4k max at WOT when the stern facing cylender fails to run... this problem came on gradually, the ski would eventually clear itself out and run pretty strong, but has become progressively worse... spark appears consistent on all three, so i assumed carbs...

    fuel filter is 4 years old, perhaps its a fuel delivery problem due to ethanol buildup? i'll try a new filter but doubt that will change anything...

    any ideas?

  7. #7
    thanks... would greatly appreciate seeing any photos you may have and are willing to share!!!!

  8. #8
    witness140's Avatar
    Join Date
    Aug 2010
    Ok, before you go tearing into this thing, slow down for a minute and let's just analyze what we have going on. Tearing into those carbs without reason is a lot of work. It is also a very dangerous place to be if you aren't careful. If you spend a few long nights reading all the posts on Ultras, you will quickly realize they are very easy to kill.

    Have you checked that all your sliders are opening when throttle is applied?

    Have you checked that all of your butterflies are all opening proportional to throttle tension?

    Have you done anything else to this ski mechanically?

    What is the ski's history. Is this something that just started? Something that has always happened? If so - how long has it been going on?

    What are the compressions?

    I have a ton of photos of an Ultra carb tear-down.

    The heart of the Ultra carb is the vacuum slider / diaphragm. They are $110 each and are not included in any rebuild kit. During a typical CV carb teardown you will be faced with some stripped corroded phillips head screws, maybe some bad gaskets or regulator diaphragms as well. The vacuum sliders should clean up nice, as should all the passages and circuits.

    A good carb cleaning is probably in order since the ski is aged and nobody has probably ever gone in there. However.....that being said.....there are some small things you can mess up during re-assembly that will cause $2000 of damage pretty quick.

    So let's back up and try to understand more of how this all unfolded and what the current stats on the ski are.

  9. #9
    witness140's Avatar
    Join Date
    Aug 2010
    Also - do you have a service manual? If not get it here.

    If you do insist on ripping into the carbs, I would take them out first and decide what you need. If you just want to do a cleaning, you can get away with nothing. If you want to do the essentials, here's what I would advise replacing. Go to and grab the 1999 JH1200 carb parts diagram and use that to work through this list.

    92055 These are little O-ring seals. They are usually fine, but at $4 each why not.
    92009C These hold down the vacuum valve guides. They are usually corroded. I'd plan on grabbing some replacements. Best bet would be to convert to hex heads so that you never strip them in the future. Up to you.
    92009E These are special phillips bolts with bushings. You will probably wreck a couple on teardown.
    11060 Gasket
    43028 Regulator Diaphragm
    43049 Thin gasket that goes under the plate in the regulator.

    If you get it open and it's a complete mess - looks like someone has bent the float arms etc, then you might need more. Or if the tip of the float needle looks worn, you might need that.

    Definitely replace the carb base gaskets. DO NOT RE-USE.
    Replace your oil lines while you are doing this because it's easier. 1/8" ID Tygon will suffice. You can grab that at a local powertool store (chainsaws, lawnmowers, that kinda place) I've even heard of autozone having it.

    THat above list of carb parts w/o the screws is about $165 in my cart. (x3 on each part) That is what I will grab when I do my other Ultra in the Fall.

  10. #10
    Here are the photos of my carb taken apart for your reference. the last one is the torn diaphragm I had.

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