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Thoughts on what to do.

Discussion in 'XJ Technical Chat' started by Metalliccurrent, Mar 17, 2017.

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  1. Timbox

    Timbox Well-Known Member

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    You might be really happy just doing the top end? If you can find a good price on the rings and other parts it would mostly only cost time. I think a lot of the bikes that have 30K or above that were not maintained have lots of carbon. Once you pull the jugs you would be able to see how the inside of the engine looks and make a call from there. Good luck either way and just keep wrenching on her.
     
    Timbox, Mar 28, 2017
    #21
  2. Metalliccurrent

    Metalliccurrent Member

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    I wanted to keep her stock but guys I found alot more 750 yics than 650. They are a cheaper price too. I know there is probably a thread on what I need to modify from 650 to 750. Can someone direct me please. Or give some first-hand insight.
     
    Metalliccurrent, Mar 28, 2017
    #22
  3. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Engine swap info, and much more, here: http://www.xjbikes.com/forums/threads/the-information-overload-hour.27544/
     
    k-moe, Mar 28, 2017
    #23
  4. Metalliccurrent

    Metalliccurrent Member

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    Wonderful thank you k-moe.
     
    Metalliccurrent, Mar 28, 2017
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  5. Metalliccurrent

    Metalliccurrent Member

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    Update, I'm picking up yics750 this weekend end. If I rebuild my 650 carbs with this kit they should run my 750 right?
    Fit Hitachi HSC32 Carbs

    Float bowl gasket
    2.0 Float needle and seat
    Y403S Slide needle
    #112, #122 and #43 jets
    Mixture screw, spring, washer and o-ring
     
    Metalliccurrent, Mar 30, 2017
    #25
  6. Metalliccurrent

    Metalliccurrent Member

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    I found these specs from church of clean thread.
    Years & Models: 1981-3 XJ750 Maxim, Midnight Maxim, and Seca USA models
    Carb Manufacturer: Hitachi
    Carb Series: HSC32
    Main FUEL Jet Size: #120
    Pilot FUEL Jet Size: #40
    Main AIR Jet Size: #80
    Pilot AIR Jet Size: #225
    AIR COMPENSATOR Jet Size: #36
    Main jet NEEDLE ID: #Y-13
    Main needle JET Size: #3.2mm (the main needle JET is also known as the "power valve" or "emulsion tube").
    Fuel Level in float bowls: 3mm +/- 1mm (.118" +/- .039")
    going off this the kit on Ebay it will be too rich, right.
     
    Metalliccurrent, Mar 30, 2017
    #26
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  7. Toomanybikes

    Toomanybikes Well-Known Member

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    US models run a little leaner than Canadian models and if you have pods or 4-1 exhaust that will change things.
    Canadian bikes had 42 pilot and 122 mains in some years
     
    Toomanybikes, Mar 30, 2017
    #27
  8. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    The only thing that needs to be changed are the jet needle and the main fuel jet. Everything else is the same. If you can get those seperately for less than the kits cost, do it.
     
    k-moe, Mar 30, 2017
    #28
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  9. Metalliccurrent

    Metalliccurrent Member

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    I sent a email to xj4ever. To help me get correct parts to do a total overhaul on carbs.
     
    Metalliccurrent, Mar 31, 2017
    #29
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  10. Metalliccurrent

    Metalliccurrent Member

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    Update:
    I went and picked up used engine over the weekend. Turns out to be a 700(696cc). Never the less it was in my price range and had better compression and less miles. It's out of a 1985 so wiring is different so I will have to re pin or get creative. Not too concerned, I'm pretty good with electronics so should be simple.
     
    Metalliccurrent, Apr 4, 2017
    #30
  11. XJ550H

    XJ550H Well-Known Member Premium Member

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    XJ550H, Apr 4, 2017
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  12. hogfiddles

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

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    You'll also find the 700 engine is a bit snappier, too
     
    hogfiddles, Apr 4, 2017
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  13. Metalliccurrent

    Metalliccurrent Member

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    Nice thanks for info. I wish I could have rode her as a 650 to compare.
     
    Metalliccurrent, Apr 4, 2017
    #33
  14. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    U.S. Government to Yamaha: "No more engines over 700cc or you pay us a big tax."

    Yamaha management to Yamaha engineering: "Can you make a 700 that's more powerful than the 750?"

    Yamaha engineering: "Easy peasy."

    Yamaha to U.S. Government: "OK."
    :)
     
    k-moe, Apr 4, 2017
    #34
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  15. Metalliccurrent

    Metalliccurrent Member

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    can someone describe proper operation of fuel petcock. It has res at 9 o'clock and works off vacuum. On at 6 o'clock and it doesn't flow fuel at all. Prime at 3 o'clock and it flows constantly. I understand Prime fills carbs but what about on,res. There is no reserve tank?
     
    Metalliccurrent, Apr 5, 2017
    #35
  16. dkavanagh

    dkavanagh Well-Known Member Premium Member

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    Does yours look like this? (this was when I had mine taken apart last summer)
    Screen Shot 2017-04-05 at 9.39.22 AM.jpg
    Res and On are both vacuum operated whereas Pri is not and used to prime the float bowls before starting the engine. I've used Pri if the bike's been sitting a while. On is where mine sits the majority of the time.
     
    dkavanagh, Apr 5, 2017
    #36
  17. XJ550H

    XJ550H Well-Known Member Premium Member

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    reserve and on work off of vac line prime is free flowing.
    there is no seperate reserve tank.
    the petcock has two intakes inside of the tank. when full and in on position it takes fuel ffrom the upper portion of the tank.
    when fuel gets low you motor will stumble you then switch to reserve and fuel flows from the lower intake.

    sounds like your petcock may be clogged or in need of rebuild if fuel does not flow in on position.
    there is a screen in the oem petcock that covers both intakes if it is an after market petcock there may be 2 screen filters.

    see this thread
    Rebuilding the Yamaha Vacuum Fuel Valve w/pics
    there is a screen in the oem petcock that covers both intakes if it is an after market petcock there may be 2 screen filters.
     
    XJ550H, Apr 5, 2017
    #37
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  18. Metalliccurrent

    Metalliccurrent Member

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    Looks just like that,
    Ok so if tank is low it will only flow from reserve. The tank is pretty much empty so I will need to fill it and check it again. I removed it and cleaned up stuck vacuum plunger. with vacuum it flows WD-40 when it's ON. I wasn't aware there was a baffle/res compartment in tank. Once I get new engine running I will fill it up and see what happens.
     
    Metalliccurrent, Apr 5, 2017
    #38
  19. XJ550H

    XJ550H Well-Known Member Premium Member

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    yes not enough gas will keep it from flowing when set to ON
    ther is no reserve/baffle compartment in the tank. just on top of the petcock there is a filter baffle

    SEE this thread for full details of the petcock
    Rebuilding the Yamaha Vacuum Fuel Valve w/pics
     
    XJ550H, Apr 5, 2017
    #39
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  20. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    There isn't a seperate reserve compartment or baffle in the tank. The main (ON) fuel draws from a taller intake tube than the reserve does.

    In this drawing the ON is the taller tube, and the RES is the shorter tube. The yellow stuff is the fuel.
    [​IMG]
     
    k-moe, Apr 5, 2017
    #40
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