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83 Seca 900 bogs down.

Discussion in 'XJ Technical Chat' started by MrSeca, May 17, 2020.

  1. Timbox

    Timbox Well-Known Member

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    +1 on this, I think there is very little room for error and how will that tape hold up to the heat and vibration? Having that tape get sucked down to the point of the jet might or might not happen.
     
  2. MrSeca

    MrSeca Active Member

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    I'm not quite sure what you guys are talking about. I'm referring to a slipping starter clutch and now we're talking about teflon tape on mixture screws. Someone bridge this gap for me.
     
  3. XJ550H

    XJ550H Well-Known Member Premium Member

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    you posted this and never said you fixed the issue
    next post was this
    so in answering the top post I suggested tef tape I will withdraw that and suggest some anti sieze to seal up threads of mix screw.
    when you try color tuning cap off the mix screw you are adjusting to see if color changes. when looking for vac leaks spray some test fluid into the mix screws see what happens

    if you feel starter clutch is going you have 2 options. ride till it goes or pull motor and change the clutch , look at chains and all guides while in there.

    so where did you get on the color tune? next size up pilot jets is an option if you have to turn mix screws out to far. only do this when you are sure there are no vac leaks
     
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  4. MrSeca

    MrSeca Active Member

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    I didn't get really any responses as far as the mixture screws so I just left them at what the PO had them at and did a carb synch. Bike is running fantastic. As far as the starter clutch, I'm just going to leave it for now. It only happens if I've been riding for a while, I park somewhere, and then turn on the bike. I'm wondering if it's a weak battery actually not having enough juice to give it a firm start. But like I said before, it NEVER happens on a cold start and I put some heavier weight oil in there 20w-50 and it still has yet to happen. At this point I'll just say the bike is perfect, except the handlebars. They're too narrow for me so I'm in the process of converting the top yoke.
     
  5. MrSeca

    MrSeca Active Member

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    I'm getting horrible gas mileage. I just came back on a 6 hour trip and I was averaging 25-30mpg going 70-75mph. I think this is kind of low. There are no leaks that I'm aware of. I turned my petcock to PRI to see if gas was overflowing out the back or the overflow tubes and there was no indication of that. As you can see in the plugs some are running a tad rich but would it make it so bad that I'm getting nearly half of the mpg as it should be?
     

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  6. Polock

    Polock Well-Known Member

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    1 good
    2 lean
    3 good
    4 little rich
    did you get it for economy or smiles per miles
     
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  7. MrSeca

    MrSeca Active Member

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    I got it because it was cool.
     
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  8. Franz

    Franz Well-Known Member

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    Your post asking about the differences in our clutches. Motorcycle Starter clutch works like this



    Motorcycle clutch works like this

     
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  9. MrSeca

    MrSeca Active Member

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    Thank you very much for that. Really cool.
     
  10. MrSeca

    MrSeca Active Member

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    Just to make sure my coils and spark plug caps are okay I ohmed them out and the readings were as follows:
    Caps
    1-7.97(ohms)
    2-4.8
    3-4.6
    4-8.11

    Coils
    1- Primary 2.8(ohms)
    Secondary 11.85

    2-Primary 2.8
    Secondary 12.54

    My only concern is with #1 and #4 plug cap as that is suppose to be between 4000 and 6000 and I'm guessing it wouldn't have much of an impact on my gas mileage. So I guess I'm opening back up those carbs.
     
  11. MrSeca

    MrSeca Active Member

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    Is there any difference in the rebuild kits between the 83 xj900 and the 85 xj900? Are the emulsion tubes and the slide needles universal or are they different lengths to fit the needs of their respective carburetor? I noticed that the jetting is the same between the different years but there may be other differences that I'm not aware of.
     
    Last edited: Jun 20, 2020
  12. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    The '85-up XJ900 models used a different series of Mikuni carbs (BS36 vs. BS35 for the 1983-84 models); the BS36 series carbs have 1mm larger throats (venturi) and differ slightly in various ways. Of course, being BS-xx series Mikuni carbs, many parts are interchangable, but there are needle differences (the BS35 series used an adjustable-position main jet needles, while the BS36 series used fixed-position needles). The emulsion tubes are all the same. The vacuum pistons are different, with the BS36 version being quite a bit heaver than the BS35 piston unit, and it has fewer air-bleed holes.
     
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  13. MrSeca

    MrSeca Active Member

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    Thanks Chacal. You sure do know your stuff. As far as the needle differences, are they the same length? Do they attach differently?
     
  14. MrSeca

    MrSeca Active Member

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    I just checked the float height on carbs 1 and 4 using the clear tube method. I think they may be too low. What do you think and what's the drawback of having them too low?
     

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  15. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    Can run lean sometimes... Could starve if you’re heavy on the throttle....
     
  16. MrSeca

    MrSeca Active Member

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    so you do agree that they are kind of low?
     
  17. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    You’d have to do a fuel level check
     
  18. Franz

    Franz Well-Known Member

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    On the matter of your brake pads rubbing on the rotors you can slacken the bleed nipple on each caliper and push the pistons back slightly then close the bleed nipples. Then keep an eye on the master cylinder fluid level when you pump the handlebar lever when the wheels and calipers are back on and everything is bolted up. Fit the wheels and then refit the calipers, with the piston pushed back slightly they will not rub on the rotor. Suspend the calipers with a wire hook or strong string out of the way until you get the wheels on.
     
  19. Rooster53

    Rooster53 Well-Known Member Premium Member

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    When checking them on the bike you need to check the level in the clear tube at the center of the float bowl as the carbs are tilted forward. The carbs should also be level from 1 to 4 when on the center stand and on a reasonably level surface.

    upload_2020-6-22_14-40-29.png
     
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  20. MrSeca

    MrSeca Active Member

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    I figured it out. It was actually calcification of old brake fluid in the calipers preventing the pistons to move freely. Once I scraped all that away the calipers worked superb. Thanks for chiming in.
     
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