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identifying carburetor

Discussion in 'XJ Technical Chat' started by francis79, Mar 13, 2023.

  1. francis79

    francis79 New Member

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    hoping to find an answer here , i have an 85 maxim xj 700 air cooled canadian model . bike has been off the road a long time and am finally close to getting it on the go again . the original carb is not in the best shape but im sure still useable . i picked up another carb that was supposed to be off a 700 as well but it has different markings on it and have been unable to cross reference them. the markings on my fuel bowl are
    hsc 033-14
    _ _h 00
    41203 as best as i can make it out .
    the carb i picked up is in real nice shape and would like to use it instead if possible , its markings are ,
    hsc 033-13
    ijj 00
    50118
    can any body shed light if they might be interchangeable , thanks
     
  2. Jetfixer

    Jetfixer Well-Known Member

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    Click on the upper right corner of page xj4ever can help you with identifying carbs , you can IM him .
     
  3. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    The carb bodies on the 700 airhead's HSC33's are *not* interchangeable due to the configuration of vent hoses and fuel lines.
     
  4. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    #1 body: Vent on right side, fuel rail opening on right side
    #2 body: Vent on left side, fuel rail opening on both sides
    #3 body: Vent on right side, fuel rail opening on both sides
    #4 body: Vent on left side, fuel rail opening on left side
     
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  5. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    Both of the carb bowls (and hopefully their associated bodies) are HSC33 series, which are correct for XJ700 air cooled and 1984 XJ750RL models. The bodies and bowls will be physically interchangeable between those models, although there will be internal jetting differences.

    The HSC33-14 / ??H 00 is a carb from this model bike:
    Year: 1986 XJ700S 49-state
    Model: HSC33 (1NH model ID)

    while the HSC33-13 / 1JJ 00 is a carb from this model bike:
    Year: 1985 XJ700NC California
    Model: HSC33 (1JJ model ID)


    Okay, now the 1985 and 1986 carb sets differ by the presence or lack thereof of a small brass port on the left upper side of the carb body (next to / to the left of the pilot mixture screw port)....this port is oriented horizontally out of the carb body, and turns towards the rear of the bike at about a 45* angle. 1985 model carbs had this port (on all four carb bodies); 1986 models do not. I believe this is a bowl vent port, but there is disagreement about this (and if it is a bowl vent, then why did it disappear on the 1986 model carbies.........?). Some people claim it's a bowl overflow (flooding) port, but that sure is high up on the carb body to perform that function..... I think that it has something to do with emissions issues, but for the life of me I don't know what. A long (about 9") rubber fuel line is attached to each of these ports (on 1985 models) and run rearward and then downward:

    *****************

    All 1985 XJ700 non-X (air-cooled models) and all XJ750RL models with the original HSC33-series Hitachi carbs also use four sections of 6.35mm fuel line, on the short brass vacuum port coming off (horizontal and angled towards the rear) of the front left of each carb body. Be aware that these hoses run from those brass ports to "nowhere"; that is, their other ends are merely open-vented to the atmosphere. These hoses run from the vac ports, and are routed "upwards" and rear of the carb rack, and their open end rests below on the airbox. The #1 and #4 carb hoses are captured by a small bright plated clip, attached to the upper rack bracket outer screws, kind of "hidden" behind the bright carb end covers. On the #1 carb, this hose is approximately 9-1/2” long, while on carbs #2, 3, and 4 the hoses are only 7-1/2” long. All 1986 XJ700 non-X (air-cooled models) do not have these brass vacuum ports, and thus do not use these hoses.

    Yes, there is a virtual explosion of fuel lines on these carbs, user Toomanybikes shows you Toomanyhoses:

    http://www.xjbikes.com/forums/threads/thoughts-on-what-to-do.111133/page-4#post-570438

    *****************

    Now, there is also a difference between California-spec carbs and "49-state" (i.e. non-California) carbs, and that is the presence of another brass port (much larger in diameter) on the #2 carb only, again located just next to the pilot mixture screw port, and oriented vertically (pointing straight up to the sky), and this port accepts a hose that runs to a charcoal vac cannister hidden behind the right side plastic frame cover. So it's definitely an emissions port. Again, this is on all California-spec carbs, be they 1985 or 1986.

    I'm not sure whether Canadian model XJ700 carbs ever used the "California" spec carbs, since most places in the world (besides California) didn't have as stringent emissions specs.

    I think it is okay to swap Cali vs. non-Cali carbs, as if you're using the Cali carbs on a 49-state bike, you can just plug up that "emissions cannister" port on the #2 carb w/o any issues. And if you have a Cali bike, you can use a #2 non-Cali carb in that #2 position, but you'll lose the use of the emissions cannister, and all that such a situation may imply.

    And I also am not sure whether the 1985 and 1986 Canadian XJ700 carbs had that "sideways port" (1985) coming off each carb body (1985) or not (1986).

    One last thing: I recall a user (Tabaka45, if I remember correctly) had a dreadful time trying to tune his (1985, I think) carbs correctly since one of the carb bodies was a 1986 version (w/o the sideways port.....whatever it does) and resolved by finally purchasing and substituting a 1985 carb body for the incorrect 1986 version. You can search the forums for his account and go back and start reading his posts from a few years ago where he describes his problems and eventual solutions.

    EXECUTIVE SUMMARY: XJ700 air-cooled carbs are hard and finicky to tune properly (probably because it was the first year of Yamaha trying to meet more stringent emissions specs), and having all these permutations of carb styles just adds to the fun..........


    P.S. you're lucky those bowls still had their ink stampings (most don't), otherwise you'd likely never properly ID the bodies.
     
    Last edited: Mar 19, 2023
  6. francis79

    francis79 New Member

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    great info , thanks for that . Looks like i will likely have a set of carbs to sell .
     
  7. tabaka45

    tabaka45 Well-Known Member

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    I did get a set of '85 carbs on a parts bike I bought. By that time I had already been through the "86 carbs" that came on my '85 XJ700 several times. Probably because I took a shortcut or two the first couple of times. But I wanted another set of carbs and just lucked up on the '85 carbs. I remember asking Chacal what all the tubes were for since my origincl carbs didn't have them. It was then that he told me that the ones with the four tubes were the correct ones for my bike. So, I carefully went through them and replaced the seats and needles (solid brass needles), used a colortune plug to initially set the pilot screws and then adjusted as needed to get them dialed in. Other than getting the carbs beyond clean, I found that the most important part of getting them dialed in was getting the fuel levels set perfectly, dialing in the pilot screws and getting the carbs properly synced. Remember that each carb is different, and therefore each pilot screw will most likely be set differently. Mine run from slightly less that two turns open to slightly more than two turns--none more than 2 1/4.
    Here is the method I used.
    Once you get the float level correct or verified and assuming the carbs are thoroughly clean, the best way to set the pilot screws is with a colortune plug. Install the colortune plug in place of the #1 spark plug, get the engine warm and at idle. Close the pilot screw until you get white flashes which indicates lean, then open the screw until the white disappears. Repeat for all four cylinders. Install new plugs (easier to read new plugs than old one.) Ride about 20 miles or so and pull the plugs and see what they look like. You are looking for a light gray or brown color, not all white. If you do not have the light gray or brown open the pilot screw about the width of a dime. Repeat for all cylinders. Take another ride and repeat the process until you have perfect colored plugs. It took me a week or so and several adjustments to get the right color, but the engine runs much better and my miles per gal went up. I know that 2 1/2 turns open is the base adjustment a lot of folks use, but with using the colortune plug none or my pilot screws are more than 2 1/4 open and some at about 2 or slightly less. Every bike and carb will be different. If you don't have a colortune plug start at about 1 3/4 and make adjustments as needed.
    After getting my carbs dialed in I have had zero problems with the carbs, and the bike starts easily, runs great and my mpg went up to about 41 mpg average. I had been getting around 35 mpg. By the way, my bike is bone stock, right down to the paper air filter.
     
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