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Carburetor Install

Discussion in 'XJ Technical Chat' started by DaRealSanti, Jul 12, 2023.

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  1. DaRealSanti

    DaRealSanti New Member

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    I am installing my Carbs and I didn't take any pictures of it installed... like a dummy. The hoses that are running out of the carb... I think there's 5 of them. I'm assuming they are some kind of fuel line/ breathing hose. Where do the get connected to IF at all? Does someone have a picture/diagram they could share? I have a service manual but the pictures are black and white, blurry and the instructions don't say.
     
  2. DaRealSanti

    DaRealSanti New Member

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    it's an 85 XJ700, hitachi HSC33 carbs. (idk if that is useful)
     
  3. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    Yes, that is very useful. These HSC33's are kind of a special animal with lots of hoses.

    If you dig around the site you can find some information. Here's a starting point:
    https://www.xjbikes.com/forums/thre...hi-carb-vent-hose-routing.130016/#post-659135

    Each carb has a vent hose near the top, and there are fuel overflow hoses between 1&2 and 3&4. These all just go to nowhere. Then of course the fuel input line.

    There is also a description of the hoses somewhere in here:
    https://www.xjbikes.com/forums/threads/xj-parts-catalog-section-c-fuel-system.44642/
     
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  4. tabaka45

    tabaka45 Well-Known Member

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    All the hoses on my XJ700 exit behind and below the engine on the brake side. Seems like there are a couple of clamps that hold them in place an they are all bunched together.
     
  5. tabaka45

    tabaka45 Well-Known Member

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    This is an old reply from Chacal.
    1. Well, that is a REALLY good question....as you're about to see. The factory manuals---owners, service, and parts manuals---are all sort of cryptic on this issue.

      The 700 Hitachi HSC33 carbs differ from the 650/750 HSC32 carbs in that there are two types of vents built into the carbs:

      a) one type, which I believe are the bowl vents, are located towards the rear of the carbs, in-between each set of carbs. These vents have a pivoting "T" connector......similar to the main fuel supply inlet located between carbs 2 & 3........and there are two of these T's, one each between carbs 1 & 2, and the other between carbs 3 & 4. These "bowl vent" T's are much laarger in OD (5/16") than the fuel supply T-connector (1/4") and are thus easy to distinguish.

      b) there are also 4 brass pipes, 1 on each carb body, pressed into the carb body just below and to the left of the idle mixture screw casting/passage. These brass nipples accept a 1/4" hose.


      Let me state right now that I do not know whether the above features are common to both XJ700N/S 49-state models AND XJ700NC/SC california-only models, but I believe they are.

      Anyway, continuing: California models use an emissions/fuel vapor recovery cannister, which is probably just filled with charcol powder or some other such substance, and this cannister has two intake ports (nipples) on top, and one outler port at the bottom.

      The owner's manual shows that one of the side covers (I think) has a small Emissions House Routing decal that shows a crude representation of the hose routing. One of the cannister intake port nipples has a hose that comes from "the fuel tank"....but don't ask me where. The other intake port nipple on the cannister shows a hose that goes to the "carb"....but doesn't show where on the carb it goes to. I would assume that this decal is applied (wherever it lives) ONLY to California model bikes, since it illustrates and mentions the vapor cannister, but who knows?

      The outlet port on the cannister goes to "atmosphere".

      The service manual is a little better, as it has not one but two cryptic diagrams concerning Emissions Hose Routing.....both a top and side view. The top view shows, again, the intake ports of the vapor cannister having one line going to the fuel tank, and the other line going to the front of one carb (???), which seems to indicate that it goes to the 1/4" brass nipple on the front of the carb, by the idle mixture screw. However, it only shows one hose going from the vapor cannister to one carb (even though two---no not 4, but 2---carbs are pictured in this illustration.

      There is also, in the service manual, a side view diagram that shows one of the vapor cannister hoses going to the front of the carb(s).

      HOWEVER, the parts manuals do not show any type of T- or Quad-connectors that would tie all four of the carb idle mixture port nipples (the brass ones, one on each carb body) together. Nor does it show any type of T-fitting that would tie those two bowl vent lines together.....the 5/16" lines that come off the two T-connector on the rear of the carb bodies 1/2 and 3/4.

      The parts manual also shows a fuel line "anti rollover valve" that fits into one of the hoses that comes off of the vapor cannister....but again, no illustration of where the one outlet of this valve leads to (one side goes to the vapor cannister via a hose).

      In all of the diagrams/illustrations, the fuel hose from the petcock outlet goes directly to the carb fuel supply inlet T-connector (between carbs 2 & 3), and the vacuum hose runs from the petcock to the #3 cylinder intake manifold, so at least the petcock is out of the loop for the emissions cannister.

      Assuming that we could figure all of the above out for the California model carbs, then the next big question would be: what did Yamaha do with all those hoses coming off the bowl vents and the four brass nipples on NON-california carbs, since there obviously wasn't a vapor cannister/anti-rollover valve to contend with on the 49-state models.

      By the way, the vapor cannister/anti-rollover valve issue appears on all XJ700 models, X and non-X, California versions. The only set of 700X carbs that I have...and I don't know whether they are the California or non-California model carbs....also have the bowl vent t-connectors (between carbs 1/2 and 3/4), but have no brass vents on each carb body up by the idle mixture screws passage (although there appears to be an undrilled port that could have been drilled and fitted with brass nipples on California models). The California and non-California X-model individual carb bodies and complete carb rack assemblies carry different factory part numbers between California and non-California models (true for both Hitachi and Mikuni carbs), but the diagrams in the parts books are identical, and show no nipples up there on either model for the X (Mikuni) carbs.....AND, besides the individual carb bodies and complete carb rack assembly part number differences between CA and non-CA carbs, ALL THE OTHER INTERNAL AND EXTERNAL PARTS ARE IDENTICAL---in other words, no jetting changes. Hmmmm......

      Also, Yamaha sometimes spells the word "carburetor" incorrectly in some versions of their manuals..........

      CONCLUSION: all a big, confusing mystery. You'd have to find an original bike that still has some of these lines intact. I'm thinking the diagrams in the manuals and parts catalogs are somewhat "generic", rushed illustrations necessary to comply with Federal laws, and the factory didn't have the time, ability, or desire to provide adequate, model-by-model drawings or photographs.

      But if you or anyone else really does know, please do share!

      http://xjbikes.com/forums/index.php?forums/xj4ever-supporting-vendor.23

      info@xj4ever.com
      http://www.xj4ever.com/
      chacal, Jan 1, 2008Report
      #4Like+ Quo
     

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